BECC-105 Solved Assignment
INTERMEDIATE MICROECONOMICS – I
Assignment 1
1.(a) Explain the term Budget constraint? If the income of the consumer increases and one of the prices of the commodity decreases at the same time, will the consumer necessarily be at least as well off? Illustrate with diagram.
(b) What is utility function? Distinguish between direct utility function and indirect utility function. State the mathematical expressions of utility function of perfect substitutes and perfect compliments.
2 (a) What do you mean by ‘Cost minimisation’. Explain the various approaches of cost minimisation, Give illustration in support of your answer.
(b) Given the total cost function
(b) What is utility function? Distinguish between direct utility function and indirect utility function. State the mathematical expressions of utility function of perfect substitutes and perfect compliments.
2 (a) What do you mean by ‘Cost minimisation’. Explain the various approaches of cost minimisation, Give illustration in support of your answer.
(b) Given the total cost function
Find (i) The Average cost function (ii) The critical value at which AC is minimized (iii) The Marginal Cost
Assignment 2
- Given the profit function
pi=160 x-3x^(2)-2xy-2y^(2)+120 y-18 \pi=160 x-3 x^2-2 x y-2 y^2+120 y-18 for a firm producing two goods x and y
Find out (i) the maximizing profits
(ii) test the second order condition. - Distinguish between price elasticity of demand and income elasticity of demand. Given
Q=700 \mathrm{Q}=700 –
Find out (i) the price elasticity of demand and
(ii) Income elasticity of demand.
5. Do you think that Walrasian equilibrium is Pareto optimal? Give reasons and proof in support of your answer.
Assignment 3
- Explain the properties of preferences with example.
- What is consumer surplus? State the relationship between consumer surplus, compensating variation and equivalent variation.
- What is risk aversion? How does insurance help in reducing risk? Illustrate.
- What is CES production function? How does CES production function approaches a Leontief Production function?
- Make distinction between any three of the following:
(i) Concave function and convex function.
(ii) Expected value and Expected utility.
(iii) General equilibrium and partial equilibrium.
(iv) Marginal Rate of Substitution and Marginal Rate of Technical Substitution.
Expert Answer:
Assignment 1
Question:-01(a)
Explain the term Budget constraint? If the income of the consumer increases and one of the prices of the commodity decreases at the same time, will the consumer necessarily be at least as well off? Illustrate with diagram.
Answer:
Budget Constraint
A budget constraint represents the combination of goods and services that a consumer can purchase given their income and the prices of those goods and services. It is typically depicted as a line on a graph where one axis represents the quantity of one good and the other axis represents the quantity of another good. The budget constraint shows all the possible combinations of two goods that a consumer can buy when spending all of their income.
Mathematically, the budget constraint is written as:
Where:
P_(1) P_1 andP_(2) P_2 are the prices of goods 1 and 2.X_(1) X_1 andX_(2) X_2 are the quantities of goods 1 and 2.I I is the consumer’s income.
Impact of Income Increase and Price Decrease
If the consumer’s income increases, their budget constraint shifts outward, allowing them to afford more of both goods. Simultaneously, if the price of one of the commodities decreases, the slope of the budget line will change, becoming less steep for that good. These two effects combined tend to increase the consumer’s purchasing power, allowing them to afford more goods or a better combination of goods than before.
Illustration with a Diagram
In the diagram below:
- The initial budget constraint (BC1) represents the consumer’s original income and prices.
- When the consumer’s income increases and the price of one good decreases, the budget constraint shifts outward (BC2).
This shift allows the consumer to move to a higher indifference curve, representing a higher level of satisfaction or utility, assuming rational consumer behavior. In most cases, the consumer will be at least as well off as before.

The diagram above shows the impact of an increase in income and a decrease in the price of one good on the budget constraint.
- The blue line represents the initial budget constraint, which shows the combinations of goods the consumer can afford with their initial income and prices.
- The green dashed line represents the new budget constraint after the consumer’s income increases and the price of one good decreases.
As we can see, the new budget constraint (green) lies outward compared to the initial one (blue), meaning the consumer can afford more of both goods. This shift generally implies that the consumer is at least as well off, and potentially better off, since they can now access more preferred combinations of goods.
Question:-01(b)
What is utility function? Distinguish between direct utility function and indirect utility function. State the mathematical expressions of utility function of perfect substitutes and perfect complements.
Answer:
Utility Function
A utility function represents a consumer’s preferences by assigning a numerical value (utility) to different bundles of goods. It measures the satisfaction or happiness a consumer derives from consuming certain quantities of goods or services.
The utility function is usually expressed as:
Where:
X_(1),X_(2),…,X_(n) X_1, X_2, …, X_n represent the quantities of different goods consumed.U U is the utility derived from the consumption bundle(X_(1),X_(2),…,X_(n)) (X_1, X_2, …, X_n) .
Direct Utility Function vs. Indirect Utility Function
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Direct Utility Function:
- The direct utility function describes the utility derived directly from the consumption of goods and services. It focuses on how much utility the consumer gets from different consumption bundles, assuming they have certain quantities of goods.
- It can be expressed as:
U(X_(1),X_(2),…,X_(n)) U(X_1, X_2, …, X_n) - The direct utility function does not consider the prices of goods or the consumer’s income but purely reflects their preferences.
-
Indirect Utility Function:
- The indirect utility function describes the maximum utility that a consumer can achieve given their income and the prices of goods. It takes into account the consumer’s budget constraint.
- The indirect utility function is derived from the optimization of the consumer’s utility under the budget constraint and is expressed as:
V(I,P_(1),P_(2),…,P_(n)) V(I, P_1, P_2, …, P_n) - Where
I I is the consumer’s income andP_(1),P_(2),…,P_(n) P_1, P_2, …, P_n are the prices of the goods. - It represents the highest level of utility that can be attained given income and prices.
Utility Functions for Perfect Substitutes and Perfect Complements
1. Perfect Substitutes:
- Goods are considered perfect substitutes when a consumer is willing to substitute one good for another at a constant rate.
- The utility function for perfect substitutes is usually of the form:
U(X_(1),X_(2))=aX_(1)+bX_(2) U(X_1, X_2) = aX_1 + bX_2 - Where
a a andb b are constants representing the rate at which one good can be substituted for the other without changing the overall utility.
2. Perfect Complements:
- Goods are considered perfect complements when they are always consumed together in fixed proportions, such as left and right shoes.
- The utility function for perfect complements is typically of the form:
U(X_(1),X_(2))=min(aX_(1),bX_(2)) U(X_1, X_2) = \min(aX_1, bX_2) - Here,
a a andb b are constants that indicate the fixed proportion in which the goods must be consumed to generate utility.
Summary of Mathematical Expressions
- Perfect Substitutes Utility Function:
U(X_(1),X_(2))=aX_(1)+bX_(2) U(X_1, X_2) = aX_1 + bX_2 - Perfect Complements Utility Function:
U(X_(1),X_(2))=min(aX_(1),bX_(2)) U(X_1, X_2) = \min(aX_1, bX_2)
These functions represent different consumer preferences regarding how they value goods either as substitutes or complements.
Question:-02(a)
What do you mean by ‘Cost minimisation’? Explain the various approaches of cost minimisation, Give illustration in support of your answer.
Answer:
Cost Minimization
Cost minimization refers to the process by which a firm determines the most cost-efficient combination of inputs (such as labor, capital, raw materials, etc.) to produce a given level of output. The goal is to minimize the total cost of production while maintaining the desired output level.
Firms are assumed to be profit-maximizing entities, and minimizing production costs is a critical step toward maximizing profits. This concept is central in economics and managerial decision-making, where firms seek to produce at the lowest possible cost for a given level of output.
Approaches to Cost Minimization
There are two main approaches to cost minimization:
- Isoquant-Isocost Approach
- Marginal Product Approach
1. Isoquant-Isocost Approach
This is a graphical approach to cost minimization. It involves using two key concepts: isoquants and isocost lines.
-
Isoquant: An isoquant represents all combinations of two inputs (say labor and capital) that can produce a given level of output. It is similar to an indifference curve in utility analysis but applies to production.
-
Isocost Line: An isocost line represents all combinations of two inputs that have the same total cost. The equation for an isocost line is:
C=wL+rK C = wL + rK Where:C C is the total cost,w w is the wage rate (cost of labor),r r is the rental rate of capital (cost of capital),L L is the quantity of labor,K K is the quantity of capital.
The goal of the firm is to find the point where an isoquant (representing a given output level) is tangent to an isocost line (representing the minimum cost of inputs). This tangency condition is where the firm is producing the given output at the minimum possible cost.
The mathematical condition for cost minimization is:
Where:
MP_(L) MP_L is the marginal product of labor,MP_(K) MP_K is the marginal product of capital.
This condition implies that the firm should allocate its inputs such that the marginal product per dollar spent on each input is equal.
2. Marginal Product Approach
This approach is based on comparing the marginal products of the inputs relative to their costs. The firm will adjust its input usage until the marginal product per dollar spent is equalized across all inputs. This method is often applied analytically rather than graphically and is based on the following rules:
- If the marginal product per dollar of labor is higher than that of capital, the firm should hire more labor and use less capital.
- If the marginal product per dollar of capital is higher than that of labor, the firm should use more capital and less labor.
The goal is to balance the cost per unit of output across inputs.
Illustration of Cost Minimization
Consider a firm that produces a fixed level of output (say 100 units) using labor and capital. The firm’s objective is to minimize the cost of producing this output level.
- Labor costs: $10 per unit.
- Capital costs: $20 per unit.
- The firm needs to decide how much labor and capital to use to produce 100 units of output.
Step 1: Isoquant and Isocost Curves
- The isoquant curve shows different combinations of labor and capital that can produce 100 units of output.
- The isocost line shows different combinations of labor and capital that can be hired for a given total cost.
Step 2: Tangency Condition
- The cost-minimizing point occurs where the isoquant for 100 units of output is tangent to the isocost line. At this point, the marginal rate of technical substitution (MRTS) of labor for capital is equal to the ratio of the prices of labor and capital:
(MP_(L))/(MP_(K))=(w)/(r) \frac{MP_L}{MP_K} = \frac{w}{r}
Step 3: Optimal Input Mix
- Suppose at the tangency point, the firm uses 5 units of labor and 3 units of capital to produce the 100 units of output. The total cost at this point is:
“Total Cost”=wL+rK=(10 xx5)+(20 xx3)=50+60=110 \text{Total Cost} = wL + rK = (10 \times 5) + (20 \times 3) = 50 + 60 = 110 - This combination minimizes the total cost of production for 100 units of output.

The diagram above illustrates the isoquant and isocost lines in the cost minimization problem:
- The blue curve is the isoquant, representing all the combinations of labor and capital that produce a given level of output (100 units in this case).
- The green dashed line is the isocost line, which shows all combinations of labor and capital that result in a total cost of $110.
The point where the isoquant curve is tangent to the isocost line represents the optimal combination of labor and capital that minimizes cost for the given level of output. This is where the firm achieves cost minimization while still producing the desired output.
By balancing the costs of inputs according to their marginal productivity, the firm ensures it is operating efficiently.
Question:-02(b)
Given the total cost function
Find:
(i) The Average cost function
(ii) The critical value at which AC is minimized
(iii) The Marginal Cost
(i) The Average cost function
(ii) The critical value at which AC is minimized
(iii) The Marginal Cost
Answer:
Let’s solve the given problem step by step:
Given Total Cost Function:
(i) The Average Cost Function
The Average Cost (AC) function is calculated by dividing the total cost (TC) by the quantity (Q):
Substituting the expression for TC TC :
Simplifying the equation:
Thus, the Average Cost function is:
(ii) The Critical Value at Which AC is Minimized
To find the critical value, we need to minimize the average cost function. To do this, we differentiate the AC function with respect to Q Q and set the derivative equal to zero.
- Differentiate the AC function:
- Set the derivative equal to zero to find the critical point:
Solving for Q Q :
Thus, the critical value at which AC is minimized is Q=2.5 Q = 2.5 .
(iii) The Marginal Cost
The Marginal Cost (MC) function is the derivative of the total cost (TC) function with respect to Q Q :
Differentiating the total cost function:
Thus, the Marginal Cost function is:
Summary of Results:
- Average Cost function (AC):
AC=Q^(2)-5Q+60 AC = Q^2 – 5Q + 60 - Critical value at which AC is minimized:
Q=2.5 Q = 2.5 - Marginal Cost function (MC):
MC=3Q^(2)-10 Q+60 MC = 3Q^2 – 10Q + 60
Assignment 2
Question:-03
Given the profit function
pi=160 x-3x^(2)-2xy-2y^(2)+120 y-18 \pi=160 x-3 x^2-2 x y-2 y^2+120 y-18 for a firm producing two goods x and y
Find out:
(i) the maximizing profits
(ii) test the second order condition.
Find out:
(i) the maximizing profits
(ii) test the second order condition.
Answer:
To solve this problem, we need to maximize the profit function given by:
(i) Finding the Maximum Profit
To find the maximizing profits, we first calculate the first-order conditions by taking the partial derivatives of the profit function with respect to x x and y y and setting them equal to zero.
- Partial derivative with respect to
x x :
- Partial derivative with respect to
y y :
Now, solve these two equations simultaneously to find the values of x x and y y .
Step 1: Solve Equation 2 for x x :
Step 2: Substitute this into Equation 1:
Step 3: Substitute y=20 y = 20 back into the expression for x x :
Thus, the maximizing values of x x and y y are x=20 x = 20 and y=20 y = 20 .
Now, substitute these values into the profit function to find the maximum profit:
Thus, the maximum profit is pi=4782 \pi = 4782 .
(ii) Testing the Second-Order Condition
To test the second-order condition, we need to verify that the profit function is concave at the critical points x=20 x = 20 and y=20 y = 20 . This involves checking the Hessian matrix of second-order partial derivatives.
- Second-order partial derivatives:
The Hessian matrix H H is:
- Determinant of the Hessian:
- Principal minors:
- The first principal minor is
H_(11)=-6 H_{11} = -6 , which is negative. - The determinant of the Hessian
“Det”(H)=20 \text{Det}(H) = 20 , which is positive.
Since the first principal minor is negative and the determinant of the Hessian is positive, the Hessian is negative definite. This satisfies the second-order condition for a local maximum.
Conclusion
- The maximizing profit is
pi=4782 \pi = 4782 atx=20 x = 20 andy=20 y = 20 . - The second-order condition is satisfied, confirming that this is a maximum point.
Question:-04
Distinguish between price elasticity of demand and income elasticity of demand. Given Q=700 \mathrm{Q}=700 –
2P+0.02y 2 \mathrm{P}+0.02 \mathrm{y} , where P=25 \mathrm{P}=25 , and y=500 \mathrm{y}=500
Find out:
(i) the price elasticity of demand
(ii) Income elasticity of demand.
Find out:
(i) the price elasticity of demand
(ii) Income elasticity of demand.
Answer:
Price Elasticity of Demand vs. Income Elasticity of Demand
Price Elasticity of Demand (PED) measures the responsiveness of the quantity demanded of a good to a change in its price. It is calculated as the percentage change in quantity demanded divided by the percentage change in price:
Income Elasticity of Demand (YED) measures the responsiveness of the quantity demanded of a good to a change in consumers’ income. It is calculated as the percentage change in quantity demanded divided by the percentage change in income:
Given Information:
Where:
P=25 P = 25 y=500 y = 500
Let’s first compute the values of Q Q , (del Q)/(del P) \frac{\partial Q}{\partial P} , and (del Q)/(del y) \frac{\partial Q}{\partial y} using the given information.
Step 1: Calculate the Quantity Demanded (Q)
Substituting P=25 P = 25 and y=500 y = 500 into the demand function:
(i) Price Elasticity of Demand (PED)
- First, calculate the partial derivative of
Q Q with respect toP P :
- Now, use the formula for Price Elasticity of Demand:
Substituting the values:
Thus, the price elasticity of demand is approximately -0.076 -0.076 .
(ii) Income Elasticity of Demand (YED)
- First, calculate the partial derivative of
Q Q with respect toy y :
- Now, use the formula for Income Elasticity of Demand:
Substituting the values:
Thus, the income elasticity of demand is approximately 0.015 0.015 .
Summary:
- Price Elasticity of Demand (PED):
-0.076 -0.076 - Income Elasticity of Demand (YED):
0.015 0.015
Question:-05
Do you think that Walrasian equilibrium is Pareto optimal? Give reasons and proof in support of your answer.
Answer:
Walrasian Equilibrium and Pareto Optimality
The question of whether Walrasian equilibrium (or competitive equilibrium) is Pareto optimal is a central topic in microeconomic theory. The answer is yes: Walrasian equilibrium is Pareto optimal under certain assumptions. Let’s discuss the reasoning and the formal proof behind this conclusion.
Definition of Walrasian Equilibrium
A Walrasian equilibrium occurs in a perfectly competitive market where every agent (consumer or firm) maximizes their utility or profit, and markets clear (demand equals supply) at a set of prices. Formally, in a Walrasian equilibrium:
- Consumers maximize utility subject to their budget constraints.
- Firms maximize profit subject to production constraints.
- Market clearing conditions are satisfied (i.e., total demand equals total supply for each good).
Definition of Pareto Optimality
An allocation is said to be Pareto optimal (or Pareto efficient) if it is impossible to make any individual better off without making at least one other individual worse off. In other words, resources are allocated in the most efficient way possible.
The First Fundamental Theorem of Welfare Economics
The key theorem linking Walrasian equilibrium to Pareto optimality is The First Fundamental Theorem of Welfare Economics. It states that:
- Every Walrasian (competitive) equilibrium is Pareto optimal, provided that certain conditions hold, including:
- Perfect competition: No individual agent has the power to influence prices.
- Complete markets: Every possible good or service is traded.
- No externalities: Consumption or production of goods does not directly affect other agents.
- Convex preferences and production sets: Consumers have convex preferences (indifference curves are convex to the origin), and production sets are convex.
Proof of Pareto Optimality in Walrasian Equilibrium
Consider an economy with consumers and firms. Let p p represent the price vector, and let x_(i) x_i be the allocation of goods to consumer i i .
Step 1: Utility Maximization
In a Walrasian equilibrium, each consumer maximizes their utility subject to their budget constraint:
Where:
U_(i)(x_(i)) U_i(x_i) is the utility function of consumeri i ,p p is the price vector,e_(i) e_i is the endowment vector for consumeri i .
The consumer chooses an optimal bundle x_(i)^(**) x_i^* , given prices p p , such that the bundle maximizes their utility.
Step 2: Profit Maximization
Each firm maximizes its profit subject to its production function. Given prices p p , each firm chooses an output level y_(j) y_j that maximizes its profit:
Where:
y_(j) y_j is the output level of firmj j ,C_(j)(y_(j)) C_j(y_j) is the cost of producing outputy_(j) y_j .
The firm chooses an optimal production level y_(j)^(**) y_j^* , given prices p p .
Step 3: Market Clearing
In a Walrasian equilibrium, markets clear, meaning the total demand for each good equals the total supply:
This condition ensures that all goods are allocated efficiently in the market.
Step 4: Proving Pareto Optimality
Suppose the allocation (x_(1)^(**),x_(2)^(**),…,x_(n)^(**)) (x_1^*, x_2^*, …, x_n^*) from the Walrasian equilibrium is not Pareto optimal. Then there exists another allocation (x_(1)^(‘),x_(2)^(‘),…,x_(n)^(‘)) (x_1′, x_2′, …, x_n’) such that:
- Some consumer is strictly better off (i.e., their utility is higher with the new allocation).
- No other consumer is worse off.
This means that some consumers can consume more than their equilibrium bundle, which violates the budget constraint for those consumers. The market-clearing condition would not hold because if one consumer consumes more, others must consume less unless the aggregate resources change. Therefore, the allocation (x_(1)^(**),x_(2)^(**),…,x_(n)^(**)) (x_1^*, x_2^*, …, x_n^*) cannot be improved without violating the budget constraint or market-clearing conditions.
Thus, a Walrasian equilibrium must be Pareto optimal because no alternative allocation can make someone better off without making someone else worse off.
Conclusion
Yes, Walrasian equilibrium is Pareto optimal, as shown by the First Fundamental Theorem of Welfare Economics. The reasoning behind this is that, under perfect competition, consumers and firms maximize their respective objectives subject to constraints, and markets clear. Therefore, no reallocation of resources can make anyone better off without harming someone else.
Assignment 3
Question:-06
Explain the properties of preferences with example.
Answer:
Preferences are a fundamental concept in consumer theory, representing how individuals rank different bundles of goods based on their desirability. Preferences are typically assumed to have certain properties that make it easier to analyze consumer behavior and make predictions about their choices. Here are the key properties of preferences, along with examples:
1. Completeness
-
Definition: Preferences are complete if, for any two bundles of goods
A A andB B , the consumer can say whether they preferA A toB B , preferB B toA A , or are indifferent between them. In other words, the consumer has a clear preference ranking for all possible bundles. -
Example: Suppose a consumer is choosing between two bundles: Bundle
A A (3 apples and 2 bananas) and BundleB B (2 apples and 3 bananas). If preferences are complete, the consumer can either:- Prefer Bundle
A A to BundleB B , - Prefer Bundle
B B to BundleA A , or - Be indifferent between them.
- Prefer Bundle
Completeness means there are no cases where the consumer is unable to compare two bundles.
2. Transitivity
-
Definition: Preferences are transitive if, for any three bundles
A A ,B B , andC C , if the consumer prefersA A toB B andB B toC C , then they must also preferA A toC C . -
Example: Suppose a consumer prefers:
- Bundle
A A (3 apples, 2 bananas) over BundleB B (2 apples, 3 bananas), - Bundle
B B over BundleC C (1 apple, 4 bananas).
- Bundle
If preferences are transitive, the consumer must also prefer Bundle A A to Bundle C C .
Transitivity ensures that the consumer’s preferences are consistent and logical.
3. Reflexivity
-
Definition: Preferences are reflexive if, for any bundle
A A , the consumer considersA A at least as good as itself. In other words, any bundle is at least as good as itself. -
Example: Bundle
A A (2 apples, 3 bananas) must be considered at least as good as BundleA A . This property is straightforward but ensures that preferences are self-consistent.
4. Monotonicity (or Non-Satiation)
-
Definition: Preferences are monotonic if more of a good is always preferred to less, assuming that all other goods remain constant. This means that "more is better" and consumers prefer larger quantities of goods.
-
Example: A consumer has a choice between two bundles:
- Bundle
A A : 3 apples, 2 bananas, - Bundle
B B : 4 apples, 2 bananas.
- Bundle
If preferences are monotonic, the consumer will prefer Bundle B B because it contains more apples while keeping the number of bananas the same.
Monotonicity implies that consumers will always want to increase their consumption if possible.
5. Convexity
-
Definition: Preferences are convex if consumers prefer averages or combinations of goods to extremes. This implies that consumers prefer diversified bundles of goods rather than putting all resources into one good.
-
Example: Suppose a consumer has the following choice between two bundles:
- Bundle
A A : 6 apples, 0 bananas, - Bundle
B B : 0 apples, 6 bananas.
- Bundle
If preferences are convex, the consumer would prefer a combination of the two, such as:
- Bundle
C C : 3 apples, 3 bananas,
because it offers a mix of both goods, which is more satisfying than an extreme bundle of only one good.
Convexity ensures that consumers prefer balanced consumption and dislike extremes.
6. Continuity
-
Definition: Preferences are continuous if small changes in the quantities of goods do not cause sudden jumps in the ranking of bundles. That is, if Bundle
A A is preferred to BundleB B , then bundles very close toA A should also be preferred toB B . -
Example: If a consumer prefers a bundle of 4 apples and 3 bananas over a bundle of 3 apples and 3 bananas, they should also prefer a bundle of 3.9 apples and 3 bananas over 3 apples and 3 bananas. Small changes in quantities should not lead to a sudden switch in preferences.
Continuity ensures that preferences change smoothly with changes in the quantity of goods.
Example of Preferences with All Properties
Consider a consumer choosing between bundles of two goods, say apples and bananas. Here are three bundles:
- Bundle
A A : 3 apples, 2 bananas - Bundle
B B : 2 apples, 3 bananas - Bundle
C C : 1 apple, 4 bananas
Complete Preferences: The consumer can rank all bundles, for example:
A A is preferred toB B ,B B is preferred toC C .
Transitive Preferences: If A A is preferred to B B and B B is preferred to C C , then the consumer also prefers A A to C C .
Reflexive Preferences: The consumer considers any bundle to be at least as good as itself, so Bundle A A is at least as good as Bundle A A .
Monotonic Preferences: If another bundle D D had 4 apples and 2 bananas, the consumer would prefer D D over A A since it has more apples with the same amount of bananas.
Convex Preferences: The consumer would prefer a balanced bundle, such as 2.5 apples and 2.5 bananas, over extreme bundles like only apples or only bananas.
Continuous Preferences: If the consumer prefers Bundle A A over Bundle B B , they will also prefer bundles slightly different from A A , such as 3.1 apples and 2 bananas, over Bundle B B .
Question:-07
What is consumer surplus? State the relationship between consumer surplus, compensating variation, and equivalent variation.
Answer:
Consumer Surplus
Consumer surplus is the difference between what consumers are willing to pay for a good and what they actually pay. It represents the extra benefit (or surplus) that consumers receive when they purchase a product for a price lower than the maximum amount they are willing to pay.
Graphically, consumer surplus is depicted as the area under the demand curve and above the price line, up to the quantity purchased.
- Example: If a consumer is willing to pay $100 for a product but buys it for $80, the consumer surplus is $20.
Compensating Variation and Equivalent Variation
Both compensating variation (CV) and equivalent variation (EV) are measures of changes in consumer welfare due to price changes or policy interventions. These concepts are closely related to consumer surplus, but they involve different ways of measuring changes in welfare.
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Compensating Variation (CV):
-
Definition: Compensating variation is the amount of money that would need to be given to a consumer after a price increase (or taken away after a price decrease) to compensate them for the price change, so they reach their original utility level.
-
Interpretation: It measures how much compensation is needed to offset the harm from a price increase or how much benefit is gained from a price decrease.
-
Example: If the price of a good rises, compensating variation is the amount of money that must be given to the consumer to make them as well off as they were before the price increase.
-
-
Equivalent Variation (EV):
-
Definition: Equivalent variation is the amount of money that would need to be taken away from (or given to) the consumer before a price change occurs so that they would be as well off as after the price change.
-
Interpretation: It measures how much money would have to be taken from the consumer to make them as bad off as they would be after a price increase or how much money would need to be given to them to match the welfare gain from a price decrease.
-
Example: If the price of a good rises, equivalent variation is the amount of money that would need to be taken from the consumer (before the price rise) to make them as bad off as they would be after the price rise.
-
Relationship Between Consumer Surplus, Compensating Variation, and Equivalent Variation
Consumer surplus, compensating variation, and equivalent variation are all measures of welfare changes due to price changes, but they measure this change in different ways:
-
Consumer Surplus (CS): This is a simpler, more commonly used measure of welfare changes and is based on the consumer’s demand curve. It measures the area between the demand curve and the price line but assumes no changes in income or utility.
-
Compensating Variation (CV): This measures how much compensation is needed to restore the consumer to their original utility level after a price change. CV focuses on the consumer’s post-change utility level and ensures that the consumer is made as well off as they were before the price change.
-
Equivalent Variation (EV): This measures how much money would have to be taken away from (or given to) the consumer to bring them to the same utility level as after the price change. EV focuses on the consumer’s pre-change utility level and asks how much income would equate to the change in welfare.
Key Points of Relationship:
-
Direction of Measurement:
- CS measures the direct difference between what consumers are willing to pay and what they actually pay, without considering income effects or utility changes.
- CV measures how much compensation would restore consumers to their original welfare (after the price change).
- EV measures how much income would equate to the change in utility before the price change occurs.
-
Ordering:
- For a price increase:
EV > CS > CV EV > CS > CV - For a price decrease:
CV > CS > EV CV > CS > EV
This ordering reflects the fact that CV and EV take into account the full welfare impact of price changes, including income effects, whereas consumer surplus is a simpler approximation. - For a price increase:
Graphical Illustration:
- Consumer Surplus (CS) is the area between the demand curve and the price line.
- Compensating Variation (CV) measures the change in income that would compensate for the change in utility after the price change.
- Equivalent Variation (EV) measures the change in income that would be needed before the price change to bring the consumer to the same utility level they would experience after the price change.
Summary:
- Consumer Surplus: Measures the net benefit consumers receive from purchasing a good at a lower price than they are willing to pay.
- Compensating Variation (CV): Measures how much income is needed to restore the consumer to their original utility level after a price change.
- Equivalent Variation (EV): Measures how much income would equate to the change in utility before the price change occurs.
All three concepts capture different aspects of welfare changes due to price variations but offer different perspectives on how much money is needed to maintain or achieve specific utility levels before or after the price change.
Question:-08
What is risk aversion? How does insurance help in reducing risk? Illustrate.
Answer:
Risk Aversion
Risk aversion refers to the behavior of consumers or investors who, when faced with uncertain outcomes, prefer to avoid risk. A risk-averse individual prefers a certain outcome over a gamble with the same expected value but some degree of uncertainty. In other words, risk-averse people value the certainty of a lower return over the possibility of a higher return with associated risk.
The degree of risk aversion is often represented by the shape of an individual’s utility function. For a risk-averse person, the utility function is concave, meaning that as wealth increases, the additional satisfaction or utility derived from an additional dollar decreases. This diminishing marginal utility of wealth leads risk-averse individuals to prefer certainty over risky scenarios.
Example:
Consider two options for an individual:
- A certain gain of $50.
- A gamble with a 50% chance of winning $100 and a 50% chance of winning nothing.
Although the expected value of the gamble is the same as the certain gain (i.e., $50), a risk-averse person would prefer the certain $50 because they derive more satisfaction from the sure outcome than the risky one.
How Insurance Reduces Risk
Insurance helps to reduce risk by transferring the financial burden of an adverse event (such as an accident, illness, or loss) from an individual to an insurance company. The individual pays a premium in exchange for the insurer bearing the risk of a financial loss. This mechanism allows the individual to convert an uncertain financial situation (with potentially large losses) into a certain one (paying a smaller, fixed premium).
Here’s how insurance helps to reduce risk:
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Risk Pooling: Insurers pool the risk of many individuals. Not all policyholders will experience adverse events at the same time, so the insurance company can pay claims from the pool of premiums collected from all policyholders.
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Predictable Premium: For a fixed cost (the insurance premium), the individual avoids the possibility of a large financial loss. This reduction in uncertainty is particularly appealing to risk-averse individuals, as they prefer known outcomes to uncertain, potentially damaging outcomes.
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Compensation for Losses: In the event of a loss, the insurance company compensates the insured party according to the terms of the policy, thereby reducing the financial impact of the loss.
Illustration of Risk Reduction through Insurance
Let’s use an example to illustrate how insurance reduces risk:
-
Suppose an individual faces a 10% probability of incurring a loss of $10,000 (e.g., due to an accident or damage) in a given year, and a 90% probability of incurring no loss. The expected loss would be:
“Expected Loss”=(0.10 xx10,000)+(0.90 xx0)=1,000 \text{Expected Loss} = (0.10 \times 10,000) + (0.90 \times 0) = 1,000 -
Without insurance, the individual faces two possibilities:
- A 10% chance of losing $10,000.
- A 90% chance of losing nothing.
The uncertainty of this situation creates anxiety for a risk-averse individual because of the possibility of a large financial loss.
- With insurance, the individual can pay a premium of, say, $1,200 annually. In exchange, the insurance company will cover the $10,000 loss if it occurs. The individual now faces a certain outcome: paying $1,200 every year, regardless of whether the loss occurs or not.
This certainty of paying the insurance premium eliminates the risk of a significant loss, which is appealing to risk-averse individuals.
Graphical Illustration of Risk Aversion and Insurance

The graph illustrates how insurance reduces risk for a risk-averse individual:
- The blue curve represents the utility of wealth for a risk-averse individual, which is concave due to diminishing marginal utility (more wealth increases utility, but at a decreasing rate).
- The green point shows the utility at the individual’s wealth if no loss occurs.
- The red point shows the utility at the lower wealth level if a loss occurs.
- The orange point represents the expected utility without insurance, which lies between the green and red points due to the uncertainty of loss.
- The purple point represents the utility with insurance, where the individual pays a fixed premium (shown as a certain reduction in wealth).
The purple point lies above the orange point, illustrating that by paying the premium (with insurance), the individual achieves higher utility (even though their wealth is slightly lower) because they avoid the risk of a large loss. Insurance transforms uncertain outcomes into a certain outcome, which is preferred by risk-averse individuals.
Conclusion:
Insurance helps to reduce risk by offering certainty in the face of uncertain outcomes. Risk-averse individuals value this certainty, as it increases their overall utility by protecting them from large financial losses.
Question:-09
What is CES production function? How does CES production function approach a Leontief Production function?
Answer:
CES Production Function
The CES (Constant Elasticity of Substitution) production function is a type of production function that describes how output is produced by combining different inputs (such as labor and capital) with a constant elasticity of substitution between them. The general form of the CES production function is:
Where:
Q Q is the quantity of output,A A is a productivity parameter (scale factor),alpha \alpha and1-alpha 1 – \alpha are distribution parameters representing the input shares,K K is the quantity of capital,L L is the quantity of labor,rho \rho is the substitution parameter, which determines the elasticity of substitution between inputs.
The elasticity of substitution sigma \sigma between inputs is related to rho \rho by the equation:
Properties of the CES Production Function
- Elasticity of Substitution: The CES function allows for different degrees of substitutability between inputs (labor and capital). The elasticity of substitution determines how easily labor and capital can be substituted for one another in the production process.
- Special Cases: Depending on the value of
rho \rho , the CES function can represent different types of production functions:- If
rho=1 \rho = 1 , the function becomes a linear production function (perfect substitutes). - If
rho=0 \rho = 0 , the function reduces to a Cobb-Douglas production function, where the elasticity of substitution is 1. - If
rho rarr-oo \rho \to -\infty , the function approaches a Leontief production function (perfect complements).
- If
Leontief Production Function
The Leontief production function represents a situation where inputs are used in fixed proportions, meaning there is no substitutability between them. The general form of the Leontief production function is:
Where:
K K is the quantity of capital,L L is the quantity of labor,a a andb b are constants that represent the fixed input coefficients.
In the Leontief function, output is determined by the smallest input. If one input is increased while the other remains constant, output does not increase.
How CES Production Function Approaches the Leontief Production Function
The CES production function approaches the Leontief production function as the elasticity of substitution approaches zero. This happens when the substitution parameter rho \rho approaches negative infinity (rho rarr-oo) (\rho \to -\infty) .
To understand this, consider the CES function:
As rho rarr-oo \rho \to -\infty , the term inside the parentheses (alphaK^(rho)+(1-alpha)L^(rho)) (\alpha K^{\rho} + (1 – \alpha) L^{\rho}) becomes dominated by the smaller of the two inputs, since a very large negative power amplifies the difference between the two inputs. Thus, the CES function converges to:
This is the Leontief production function, where the output is determined by the minimum of the inputs, reflecting the idea that the inputs must be used in fixed proportions (no substitutability).
Example of Convergence to Leontief
Suppose the CES production function is:
As rho \rho decreases (becomes more negative), the production function becomes less substitutable. When rho rarr-oo \rho \to -\infty , the output will be determined by the minimum of K K and L L , representing a fixed proportion of inputs, which is characteristic of the Leontief function.
Conclusion
The CES production function is a flexible model that accommodates varying degrees of substitutability between inputs. When the elasticity of substitution between inputs approaches zero (as rho rarr-oo \rho \to -\infty ), the CES function converges to the Leontief production function, where inputs are used in fixed proportions and no substitution between them is possible.
Question:-10
Make distinction between any three of the following:
(i) Concave function and convex function.
(ii) Expected value and Expected utility.
(iii) General equilibrium and partial equilibrium.
(iv) Marginal Rate of Substitution and Marginal Rate of Technical Substitution.
(i) Concave function and convex function.
(ii) Expected value and Expected utility.
(iii) General equilibrium and partial equilibrium.
(iv) Marginal Rate of Substitution and Marginal Rate of Technical Substitution.
Answer:
Let’s break down each of the pairs and highlight their distinctions:
(i) Concave Function vs. Convex Function
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Concave Function:
- A function is concave if, for any two points on the function, the line segment connecting them lies below or on the function.
- Mathematically, a function
f(x) f(x) is concave if for anyx_(1) x_1 andx_(2) x_2 in its domain, and anylambda in[0,1] \lambda \in [0, 1] :f(lambdax_(1)+(1-lambda)x_(2)) >= lambda f(x_(1))+(1-lambda)f(x_(2)) f(\lambda x_1 + (1 – \lambda) x_2) \geq \lambda f(x_1) + (1 – \lambda) f(x_2) - Concave functions typically represent diminishing returns or utility in economics.
- Example:
f(x)=sqrtx f(x) = \sqrt{x} is a concave function.
-
Convex Function:
- A function is convex if, for any two points on the function, the line segment connecting them lies above or on the function.
- Mathematically, a function
f(x) f(x) is convex if for anyx_(1) x_1 andx_(2) x_2 in its domain, and anylambda in[0,1] \lambda \in [0, 1] :f(lambdax_(1)+(1-lambda)x_(2)) <= lambda f(x_(1))+(1-lambda)f(x_(2)) f(\lambda x_1 + (1 – \lambda) x_2) \leq \lambda f(x_1) + (1 – \lambda) f(x_2) - Convex functions are often used to model costs or risk in economics.
- Example:
f(x)=x^(2) f(x) = x^2 is a convex function.
(ii) Expected Value vs. Expected Utility
-
Expected Value (EV):
- The expected value of a random variable is the weighted average of all possible outcomes, with the weights being the probabilities of those outcomes.
- Mathematically, for a discrete random variable
X X with outcomesx_(i) x_i and probabilitiesp_(i) p_i , the expected value is:E(X)=sump_(i)*x_(i) E(X) = \sum p_i \cdot x_i - Example: If a coin flip yields $1 for heads and $0 for tails, with equal probability, the expected value is
E(X)=0.5*1+0.5*0=0.5 E(X) = 0.5 \cdot 1 + 0.5 \cdot 0 = 0.5 .
-
Expected Utility (EU):
- The expected utility considers the utility of different outcomes, not just their monetary value. It is the probability-weighted average of the utilities associated with each possible outcome.
- Mathematically, for a utility function
u(x) u(x) , the expected utility is:E(U)=sump_(i)*u(x_(i)) E(U) = \sum p_i \cdot u(x_i) - Example: A risk-averse person might have a utility function
u(x)=sqrtx u(x) = \sqrt{x} . If the outcomes are the same as the coin flip above, the expected utility would be:E(U)=0.5*sqrt1+0.5*sqrt0=0.5 E(U) = 0.5 \cdot \sqrt{1} + 0.5 \cdot \sqrt{0} = 0.5 - Distinction: Expected value focuses purely on the monetary outcome, while expected utility incorporates the decision-maker’s preferences and attitudes toward risk.
(iii) General Equilibrium vs. Partial Equilibrium
-
General Equilibrium:
- In general equilibrium analysis, all markets in the economy are considered simultaneously, and equilibrium is achieved when supply equals demand in all markets.
- This framework captures the interdependencies between different markets, where a change in one market affects others.
- Example: If there is a change in the price of oil, general equilibrium analysis examines not only the oil market but also the impact on labor markets, goods markets, and even international trade.
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Partial Equilibrium:
- Partial equilibrium analysis focuses on a single market or sector while assuming that other markets remain unchanged or unaffected.
- It isolates the market under study, ignoring feedback effects from other markets.
- Example: Analyzing the impact of a tax on the price of bread in the bread market without considering effects on other related markets like flour or labor.
(iv) Marginal Rate of Substitution (MRS) vs. Marginal Rate of Technical Substitution (MRTS)
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Marginal Rate of Substitution (MRS):
- The MRS measures the rate at which a consumer is willing to substitute one good for another while maintaining the same level of utility (indifference curve).
- Mathematically, the MRS between goods
X X andY Y is:MRS=-(del U//del X)/(del U//del Y) MRS = -\frac{\partial U/\partial X}{\partial U/\partial Y} - Example: If a consumer is willing to give up 2 units of good
X X for 1 unit of goodY Y while keeping utility constant, the MRS is 2.
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Marginal Rate of Technical Substitution (MRTS):
- The MRTS measures the rate at which a firm can substitute one input (e.g., labor) for another (e.g., capital) while maintaining the same level of output (isoquant curve).
- Mathematically, the MRTS between inputs
K K andL L is:MRTS=-(del Q//del K)/(del Q//del L) MRTS = -\frac{\partial Q/\partial K}{\partial Q/\partial L} - Example: If a firm can reduce capital by 3 units by employing 1 additional unit of labor without changing output, the MRTS is 3.
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Distinction:
- MRS focuses on consumer preferences and how they trade off goods to maintain utility.
- MRTS focuses on production and how a firm substitutes inputs to maintain a given output level.