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 in the long run. hour must be O A. 24 O B. 16.67 O C. 40 D. 37.5