Suppose a profit-maximizing monopolist is producing 800 units of output and is charging a price of $40

Question:

Suppose a profit-maximizing monopolist is producing 800 units of output and is charging a price of $40 per unit.
a. If the elasticity of demand for the product is 2, find the marginal cost of the last unit produced.
b. What is the firm’s percentage markup of price over marginal cost?
c. Suppose that the average cost of the last unit produced is $15 and the firm’s fixed cost is $2000. Find the firm’s profit.