please explain as well

D) none of the above 13. From the following table, determine the marginal product of labor when the firm increases from three to four units of labour input: TOTAL INPUT TOTAL PRODUCT O 15 35 50 60 65 A ) 5 B) 10 C) 15 D) 60 E) 240 14. The law of diminishing marginal returns is first evident in the following table