Question:

When a perfectly competitive industry is in long-run equilibrium, all firms in the industry

A.

earn zero economic profits

B.

produce a level of output where short-run marginal cost is equal to short-run average total cost

C.

produce a level of output where long-run marginal cost is equal to long-run average cost

D.

All of the above are correct

Answer» d. All of the above are correct