Marginal cost tells us: Select one: O a. the variable cost associated with a typical unit of output, if all variable cost is divided evenly over all the units produced O b. the marginal change in profitability when price is constant O c. the variable cost of the last unit of output, if total cost does not include a fixed cost component O d. the marginal cost of the first unit of output, if total cost is divided evenly over all the units produced