The Following Data Show the Total Output for a Firm

Multiple Choice

The following data show the total output for a firm when different amounts of labour are combined with a fixed amount of capital.Assume that the wage per unit of labour is $10 and the cost of the capital is $50.
TABLE 7-3
-Refer to Table 7-3.What is the marginal product of the 4th unit of labour hired by the firm?

A) 42
B) 60
C) 132
D) 900
E) 1320