An investor deposits $1000 into a fund on January 01, 2007. On November 01, 2007, the account balance is $900 and then $500 is deposited. On February 01, 2008, the account balance is $1500 and then the investor withdraws $800. The account balance on August 31, 2008 is $1000. Calculate the approximate annual effective dollar weighted yield for the period from January 01, 2007 to August 31, 2008.