Scenario 13-3 Suppose a Certain Competitive Firm Is Producing Q=500 Units of Units

Scenario 13-3
Suppose a certain competitive firm is producing Q=500 units of output.The marginal cost of the 500th unit is $17,and the average total cost of producing 500 units is $12.The firm sells its output for $20.
-Refer to Scenario 13-3.At Q=499,the firm's profits equal

A) $3,980.
B) $3,992.
C) $3,997.
D) $4,017.