A firm employs 100 workers at a wage rate of $10 per hour, and 50 units of capital at a rate of $20 per hour. The marginal product of labor is 3, and the marginal product of capital is 5. The firm

(a) is producing its current output level at the minimum cost.

(b) could reduce the cost of producing its current output level by employing more capital and less labor.

(c) could reduce the cost of producing its current output level by employing more labor and less capital.

(d) could increase its output at no extra cost by employing more capital and less labor

Why is the awnser c