You have the following historical annual total returns on Terlingua Oil & Gas Exploration: Annual total return Year (%) 2001 -4% 2002 -5% 2003 6% 19% 2004 2005 14% 2006 1% 2007 10% 2008 9% 2009 0% 2010 8% 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