Using the data in the following table, and the fact that the correlation of A and B is 0.18, calculate the volatility (standard deviation) of a portfolio that is 80% invested in stock A and 20% invested in stock B. Year 2008 2009 2010 2011 2012 2013 Realized Returns Stock A Stock B -7% 30% 10% 39% 10% 1% - 1% -4% 3% -7% 15% 27% The standard deviation of the portfolio is %. (Round to two decimal places.)