You have the following historical annual total returns on Terlingua Oil & Gas Exploration: Year Annual total return (%) 2001 7% 2002 -3% 2003 12% 2004 20% 2005 12% 2006 8% 2007 16% 2008 4% 2009 -13% 2010 5% Calculate the sample standard deviation of annual return. Do not round at intermediate steps in your calculation. Express your answer in percent. Round to two decimal places. Do not type the % symbol.