Returns for the Alcoff Company over the last 3 years are shown below. What's the standard deviation of the firm's returns? (Hint:This is a sample, not a complete population, so the sample standard deviation formula should be used.)

Year

Return

2010

21.00%

2009

-12.50%

2008

18.40%

Select one:

a. 18.67%

b. 18.64%

c. 18.70%

d. 18.73%

e. 18.76%