A stock will have a loss of 12.5 percent in a recession, a return of 11.2 percent in a normal economy, and a return of 25.9 percent in a boom. There is 22 percent probability of a recession, 47 percent probability of normal economy, and 31 percent probability of boom. What is the standard deviation of the stock's returns?

a)13.79%

b)19.01%

c)12.64%

d)11.82%

e)10.34%