6. In the long run, both capital and labor, as well as all other inputs to the production process of a good or service are variable. So managers have a range of choices of how much labor and capital to employ. In order to minimize costs of production in the long run, a manager should hire according to which set of criteria given below

a. They should hire the least amount of labor and the most capital equipment possible

b. They should hire both capital and labor to the point that the added output per added dollar spent on labor equals the added output per added dollar spent on capital equipment

c. They should hire the amount of capital equipment needed to maximize the productivity of labor