Assume these are the stock market and Treasury bill returns for a 5-year period: Year 2011 2012 2013 2014 2015 Stock Market T-Bill Return Return (%) (%) -36.23 2.50 29.50 0.90 15.96 0.18 1.78 0.10 17.26 0.12 a. What was the risk premium on common stock in each year? (Do not round intermediate calculations. Enter your answers as a percent rounded to 2 decimal places.) Risk Premium Year 2011 % 2012 % 2013 % 2014 % 2015 % b. What was the average risk premium? (Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places.) Average risk premium c. What was the standard deviation of the risk premium? (Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places.) Standard deviation