高階ECON-MSTR-019
In the long-run equilibrium of perfect competition, with free entry, a firm typically:
A. Makes positive economic profit forever.
B. Makes zero economic profit and produces where P = minimum ATC.✓ 答案
C. Produces where P is above ATC.
D. Shuts down because price equals marginal cost.
解說
Free entry competes economic profit away. The horizontal demand just touches ATC at its minimum, so P = MC = minimum ATC and economic profit is zero. That is not a shutdown: the firm covers all costs, including opportunity cost. Accounting profit can still be positive.