Using the data in the following table, and the fact that the correlation of A and B is 0.25, calculate the volatility (standard deviation) of a portfolio that is 50% invested in stock A and 50% invested in stock B. Year 2008 2009 2010 2011 2012 2013 Realized Returns Stock A Stock B - 15% 14% 11% 40% 10% 1% -2% - 10% -6% 25% 5% 7% The standard deviation of the portfolio is %. (Round to two decimal places.)