Essentials of Economics 7th Edition by Gregory Mankiw

Exercise 17

A profit-maximizing firm in a competitive market is currently producing 100 units of output. It has average revenue of $10, average total cost of $8, and fixed costs of $200.
a. What is profit?
b. What is marginal cost?
c. What is average variable cost?
d. Is the efficient scale of the firm more than, less than, or exactly 100 units?