Table 91 -Refer to Table 9

Table 9.1
$$\begin{array} { | c | c | c | c | } \hline \text { Quantity } & \text { Price } ( \$ ) & \begin{array} { l } \text { Total } \\\text { Revenue }\end{array} & \begin{array} { l } \text { Marginal } \\\text { Revenue }\end{array} \\\hline 1 & 50 & 50 & - \\\hline 2 & 45 & 90 & 40 \\\hline 3 & 40 & & 30 \\\hline 4 & & 140 & 20 \\\hline 5 & 30 & 150 & \\\hline\end{array}$$
-Refer to Table 9.1,which shows revenue for a monopolist.Average revenue for 4 units is _____

A) $10.
B) $120.
C) $90.
D) $35.
E) $50.