Exhibit 6-8 Bea's Total Utility of 3-Minute Telephone Calls -Refer to Exhibit 6-8

Exhibit 6-8 Bea's total utility of 3-minute telephone calls $$\begin{array} { | c | c | } \hline \begin{array} { c } \text { Quantity of } \\\text { 3-Minute Calls }\end{array} & \begin{array} { c } \text { Total Utility of } \\\text { Telephone Calls }\end{array} \\\hline 0 & 0 \\1 & 15 \\2 & 28 \\3 & 38 \\4 & 45 \\5 & 50 \\6 & 48 \\\hline\end{array}$$
-Refer to Exhibit 6-8. Bea's marginal utility of her second telephone call is:

A) 28.
B) 15.
C) 13.
D) 10.
E) 1.