Answer: Option (a) is correct.
Explanation:
Correct option: Average Total Cost (ATC)
The firm's efficient level is the quantity of output that minimizes the average total cost. Firm's efficiency is attained at a point where price is equal to marginal cost. Hence, there is one more condition where marginal cost is equal to average total cost.
It is also a point where firm can maximize its profit and total quantity of output is also maximized at this point.
∴ At this point of maximization, firm's efficient level of quantity minimizes the average total cost.
