One of your customers is delinquent on his accounts payable balance. You've mutually agreed to a repayment schedule of $400 per month. You will charge 1.4 percent per month interest on the overdue balance. If the current balance is $17,320, how long will it take for the account to be paid off? (Do not round intermediate calculations and round your answer to 2 decimal places, e.g., 32.16.)