A stock produced returns of 11 percent, 19 percent, and 2 percent over three of the past four years, respectively. The arithmetic average for the past four years is 9 percent. What is the standard deviation of the stock's returns for the four-year period?
Select one:
a. 5.46 percent
b. 8.54 percent
c. 9.09 percent
d. 6.83 percent
e. 7.70 percent