Consider a firm with a marginal cost that initially decreases, but after reaching a minimum then increases with output (that is, the more output is produced, the higher the marginal cost). Suppose the firm is producing in the short run, which implies that there are some fixed costs. Which of the following statements is correct?

a. To produce at the minimum average total cost, the firm must produce more output than it would need to produce at the minimum average variable cost.
b. To produce at the minimum average variable cost, the firm must produce more output than it would need to produce at the minimum average total cost.
c. The level of output that minimizes the average variable cost is also the level of output that minimizes the average total cost.
d. There is no level of output that minimizes the average total cost.

The total cost of a firm minimizes when a firm produces more units. Variable cost of a firm is lower when there is more output produced. The average total cost includes the average fixed cost also for which output should be more so that total fixed cost is divided to the produced units resulting in lowest possible per unit cost.