-If This Firm Were a Perfect Competitor Selling Its Entire

Multiple Choice

$$\begin{array}{l}\begin{array} { cc } \text { Units of Input}&\text { Units of Outputs }\\1 & 3 \\2 & 7 \\3 & 10 \\4 & 12 \\5 & 13 \\6 & 12\end{array}\end{array}$$
-If this firm were a perfect competitor selling its entire output at a price of $1,the marginal revenue product of the third unit of input would be

A) $0.
B) $1.
C) $2.
D) $3.
E) $10.