The correct answer is: B. MRP = MPP Ã MR
Marginal revenue product (MRP) is the additional revenue that a firm earns by employing one more unit of labor. It is calculated by multiplying the marginal physical product (MPP) of labor by the marginal revenue (MR).
The MPP of labor is the additional output that a firm produces by employing one more unit of labor. It is calculated by dividing the change in output by the change in labor input.
The MR is the additional revenue that a firm earns by selling one more unit of output. It is calculated by dividing the change in revenue by the change in output.
Therefore, the MRP of labor is equal to the MPP of labor multiplied by the MR.
Option A is incorrect because it multiplies the MRP by itself. This would make the MRP larger than it actually is.
Option C is incorrect because it adds the MPP and the MR. This would not give the correct value for the MRP.
Option D is incorrect because it adds the MPP and the MR, and then multiplies the sum by the MR. This would make the MRP larger than it actually is.