The Perfectly Competitive Widget Industry Is in Long-Run Equilibrium

The perfectly competitive widget industry is in long-run equilibrium.A profit-maximizing manufacturer receives total revenue of $55,000.He uses his labor, $15,000 worth of wire, and $15,000 worth of steel to make the widgets.The manufacturer

A) is earning an economic profit of $25,000.
B) must have an opportunity cost of labor of less than $25,000.
C) must have an opportunity cost of labor of exactly $25,000.
D) must have an opportunity cost of labor of more than $25,000.