The Number of Golf Balls Ordered by Customers of a Pro

Multiple Choice

The number of golf balls ordered by customers of a pro shop has the following probability distribution. $$\begin{array} { r | r | r | r | r | r } \mathrm { x } & 3 & 6 & 9 & 12 & 15 \\\hline \mathrm { p } ( \mathrm { x } ) & 0.14 & 0.12 & 0.36 & 0.28 & 0.10\end{array}$$

A) 6.57
B) 8.28
C) 9
D) 9.24
E) 8.82