According to the rule for maximizing profit, the highest profit is earned at the price where
A. average cost is just less than or equal to marginal revenue.
B. average cost is just less than or equal to average revenue.
C. total revenue is just greater than total costs.
D. marginal cost is just less than or equal to marginal revenue.
E. total revenue is equal to total costs.
Answer: D. marginal cost is just less than or equal to marginal revenue.