Assume these are the stock market and Treasury bill returns for a 5-year period: Stock Market T-Bil1 Return Return (%) Year 2011 2012 2013 2014 2015 -35.63 30.60 15.26 2.48 18.56 3.20 1.60 0.22 0.07 0.09 a. What was the risk premium on common stock in each year? (Do not round intermediate ce percent rounded to 2 decimal places.) Year Risk Premium 2011 2012 2013 2014 2015 b. What was the average risk premium? (Do not round intermediate calculations. Enter your decimal places.) Average risk premium