A firm is producing 100 pencils per week. The production process requires labor and capital as inputs. Labor costs $6 per labor hour and capital costs $12 per machine hour. Currently, the marginal product of labor is 18 pencils and the marginal product of capital is 36 pencils. To minimize the cost of producing this level of output the firm should use:

A. More capital and less labor

B. More labor and less capital

C. Less labor and less capital

D. the current amounts of labor and capit