When Calculating a Firm's Profit,an Economist

When calculating a firm's profit,an economist

A) will subtract only explicit costs from total revenue since these are the only costs that can be measured explicitly.
B) will subtract only implicit costs from total revenue since these include both the costs that can be directly measured as well as the costs that can be indirectly measured.
C) will subtract only the opportunity costs from total revenue since these include both the implicit and explicit costs of the firm.
D) will subtract only the marginal cost since the cost of the next unit is the only relevant cost.