$\text { TABLE } 10-1$ -Refer to Table 10- 1

$\begin{array}{|l|l|}\hline\text { Price } & \begin{array}{l}\text { Quantity } \\\text { Demanded }\end{array} \\\hline \$ 8 & 5 \\\hline \$ 7 & 6 \\\hline \$ 6 & 7 \\\hline \$ 5 & 8 \\\hline \$ 4 & 9 \\\hline \$ 3 & 10 \\\hline \$ 2 & 11 \\\hline\end{array}$
$\text { TABLE } 10-1$
-Refer to Table 10- 1. For a single- price monopolist producing and selling 9 units, the marginal revenue earned by selling the 9th unit is

A) - 2.
B) - 4.
C) 0.
D) 2.
E) 4.