Stock market and T-bill

Here are stock market and Treasury bill percentage returns between 2006 and 2010:

Year Stock Market Return T-Bill Return
2006 17.17 6.00
2007 7.31 5.86
2008 -38.73 1.70
2009 29.40 0.80
2010 19.06 0.42

a.

What was the risk premium on common stock in each year? (Negative values should be indicated by a minus sign. Round your answers to 2 decimal places.)

Year Risk Premium
2006 %
2007 %
2008 %
2009 %
2010 %

b.

What was the average risk premium? (Do not round intermediate calculations. Round your answer to 2 decimal places.)

Average risk premium %

c.

What was the standard deviation of the risk premium? (Do not round intermediate calculations. Round your answer to 2 decimal places.)

Standard deviation of the risk premium %