The Diagram Below Shows the MRP Curve for a Firm

Multiple Choice

The diagram below shows the MRP curve for a firm producing copper plumbing pipe.The factor of production being considered here is hours of labour.
FIGURE 13-1
-Refer to Figure 13-1.Suppose this firm initially has the marginal revenue product curve MRP1.One reason that the curve could shift to MRP3 is

A) an increase in demand for the firmʹs output,copper plumbing pipe.
B) a decrease in the market price of copper plumbing pipe.
C) a decrease in the supply of labour.
D) an increase in the wage rate.
E) an increase in the marginal product of labour.