A Competitive Firm Sells Its Output for $45 Per Unit

A competitive firm sells its output for $45 per unit.It employs 30 workers,and the marginal product of the 30th worker is four units of output per day.It pays its workers a wage of $150 per day.Which statement will help the firm make the right decision regarding hiring a 31st worker

A) The firm's profit would increase if it hired a 31st worker.
B) For the 30th worker, the value of the marginal product of labour is $600.
C) For the 30th worker, the marginal revenue product is $600.
D) Workers are consistently becoming more productive.