If the Long-Run Total Cost Curve for Each Firm Is

Multiple Choice

If the long-run total cost curve for each firm is given by TC = 60Q - 70Q² + 4Q³, in the long run, the marginal cost is:

A) 60 - 70Q + 4Q².
B) 60 - 140Q + 12Q².
C) 60Q - 70Q² + 4Q³.
D) -70Q² + 4Q³.