A monopolist uses one input X, which she purchases at the fixed price p=5 in order to produce output q. Her demand and production functions are: P=85-3q and q= 2×1/2 respectively. Derive the equilibrium output and equilibrium profit

To derive the equilibrium output and equilibrium profit for the monopolist, we need to find the quantity of output (q) that maximizes her profit.

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The monopolist’s profit is given by the difference between total revenue and total cost.

  1. Total Revenue (TR):

TR = P * q

TR = (85 – 3q) * (2 * x^(1/2))

TR = (85 – 3q) * (2 * x^(1/2))

  • Total Cost (TC):

TC = p * x

TC = 5 * x

  • Profit (π):

Π = TR – TC

Π = (85 – 3q) * (2 * x^(1/2)) – 5 * x

Now, we want to maximize profit, so we’ll take the derivative of the profit function with respect to q and set it equal to zero to find the equilibrium output:

Dπ/dq = 0

d/dq [(85 – 3q) * (2 * x^(1/2)) – 5 * x] = 0

First, let’s find the derivative of the profit function with respect to q:

Dπ/dq = [2 * x^(1/2)] * (-3) + (85 – 3q) * [2 * (1/2) * x^(-1/2)] = -6x^(1/2) + (85 – 3q) * x^(-1/2)

Now, set it equal to zero and solve for q:

-6x^(1/2) + (85 – 3q) * x^(-1/2) = 0

Multiply through by x^(1/2) to simplify:

-6 + (85 – 3q) = 0

Now, isolate -3q:

-3q = 6 – 85

-3q = -79

Divide by -3:

Q = 79 / 3

Q ≈ 26.33 (rounded to two decimal places)

So, the equilibrium output (q) is approximately 26.33.

To find the equilibrium profit, substitute this value of q back into the profit function:

Π = (85 – 3q) * (2 * x^(1/2)) – 5 * x

Π = (85 – 3 * 26.33) * (2 * x^(1/2)) – 5 * x

Calculate π:

Π ≈ (85 – 79) * (2 * x^(1/2)) – 5 * x

Π ≈ 6 * (2 * x^(1/2)) – 5 * x

Π ≈ 12x^(1/2) – 5x

Now, the monopolist’s equilibrium profit depends on the value of x (the input), which we don’t have information about. Therefore, you would need to know the value of x to calculate the exact equilibrium profit.

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