At a constant force of interest of 5%, a loan is being repaid with 3 payments: a payment of 3000 at the end of 10 years, a payment of 7000 at the end of 20 years, and a payment of 9000 at the end of 30 years. Compute the time T the borrower could repay the loan with a single payment of 11700. T = (Give your answer correct to 2 decimal places)