Use the Figure Below to Answer the Following Questions

Use the figure below to answer the following questions. Figure 18.3.2
-Refer to Figure 18.3.2.At an employment level of 40 hours per week,the difference in the value of marginal product of high-skilled workers and low-skilled workers is

A) $0.
B) $2 an hour.
C) $6 an hour.
D) $4 an hour.
E) $3 an hour.