Consider the Following Table for a Firm -Refer to Table 13- 2

Consider the following table for a firm. $$\begin{array}{l}\begin{array} { | l | l | } \hline \begin{array} { l } \text { Total Number of } \\\text { Units of the } \\\text { Factor }\end{array} & \begin{array} { l } \text { Total Number of } \\\text { Units of Output }\end{array} \\\hline 2 & 100 \\\hline 3 & 110 \\\hline 4 & 128 \\\hline 5 & 148 \\\hline 6 & 162 \\\hline 7 & 170 \\\hline 8 & 166 \\\hline\end{array}\\\text { TABLE 13- } 2\end{array}$$
-Refer to Table 13- 2. Suppose the firm is a perfect competitor and faces a given price of the product equal to $2 per unit. The marginal revenue product of the 5th unit of the factor is .

A) $128
B) $2
C) $40
D) $20
E) $148