Alpha Industries stock had returns of 17 percent, -11 percent, 9 percent, and 2 percent for four of the last five years, respectively. The average return of the stock over this period was 8.7 percent. What is the standard deviation of the stock's returns?

Group of answer choices

14.67 percent

12.90 percent

15.14 percent

15.47 percent

14.31 percent