As the purchaser of a new house, Carrie Underwood has signed a mortgage note to pay the Nashville National Bank and Trust Co. $8,000 every 6 months for 11 years, at the end of which time she will own the house. At the date the mortgage is signed, the purchase price was $133,109 and Underwood made a down payment of $17,500. The first payment will be made 6 months after the date the mortgage is signed. Using a financial calculator, compute the exact rate of interest earned on the mortgage by the bank. (Round answer to 2 decimal places, e.g. 25.25%.) R Rate of interest (semiannual) %