Answer the Question on the Basis of the Following Demand $\quad$

Answer the question on the basis of the following demand and cost data for a specific firm. $\quad$$\quad$$\quad$$\quad$$\text { Demand Data }$ $\quad$$\quad$$\quad$ $\text { Cost Data }$
$\begin{array}{|c|c|c|c|c|}\hline(1) &(2) &(3) &&\text { Total } \\\text { Price }&\text { Price }&\text { Quanti }&\text { Outpu }&\text { Cost } \\&&\text { ty }& \text { t }\\\hline 11.0 & \$ 10.0 & 6 & 6 & \$ 61 \\0 & 0 & & & \\\hline 9.99 & 8.85 & 7 & 7 & 62 \\\hline 9.00 & 8.00 & 8 & 8 & 64 \\\hline 8.00 & 7.00 & 9 & 9 & 67 \\\hline 7.10 & 6.10 & 10 & 10 & 72 \\\hline 6.00 & 5.00 & 11 & 11 & 79 \\\hline 5.15 & 4.15 & 12 & 12 & 86 \\\hline\end{array}$ If columns (1) and (3) of the demand data shown are this firm's demand schedule, the profit-maximizing level of output will be

A) 12 units.
B) 8 units.
C) 10 units.
D) 9 units.