Joan deposits $500 into a savings account. The account pays simple interest at an annual rate of 10% for the first 2 years. The balance at the end of 2 years then begins earning compound interest at a nominal annual rate of X%, compounded semi- annually, for the next 3 years. At the end of 2+3 years, Joan's balance is the same as if her initial deposit had earned interest at a constant annual interest of 9%, compounded yearly. What is the value of X? (Keep your answer to 2 decimal places, e.g. 43.21.)