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 16.40%

Select the correct answer. a. 18.04% b. 18.16% c. 18.07% d. 18.10% e. 18.13%