A Competitive Firm Has Been Selling Its Output for $20

Multiple Choice

A competitive firm has been selling its output for $20 per unit and has been maximizing its profit, which is positive. Then, the price falls to $18, and the firm makes whatever adjustments are necessary to maximize its profit at the now-lower price. Once the firm has adjusted, its

A) quantity of output is lower than it was previously.
B) average total cost is lower than it was previously.
C) marginal cost is higher than it was previously.
D) All of the above are correct.