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	32.80%

Select the correct answer.

a. 23.47%

b. 23.50%

c. 23.53%

d. 23.56%

e. 23.59%