Refer to the Following:
Columns 1 and 2 Make Up

Refer to the following:
Columns 1 and 2 make up a portion of a monopolist's production function for a single variable input, labor. Columns 2 and 3 represent the demand function facing the monopolist over this range of output:
$$\begin{array} { c c c } (1) & \text { (2) } & \text { (1) } \\\hline \text { Undsar Labor } & \text { Unds of Oupud } & \text { Price } \\\hline 3 & 370 & \$ 10 \\4 & 490 & 9 \\5 & 570 & 8 \\6 & 600 & 7 \\7 & 670 & 6\end{array}$$
-How much does the fifth unit of labor add to the firm's total revenue?

A) $1.875
B) $80
C) $150
D) $4,560
E) none of the above