A competitive firm is using only labour and capital as inputs, and it maximizes its profits in the long run. You know that the firm pays an hourly wage of $20 and its hourly cost of a unit of capital is $25. if this firm's marginal product of labour is 30 units per hour, then its marginal product of capital per hour must be in the long run. O A 40 OB 16.67 OC. 37.5 OD 24