I need formula of number months until paid off, rather than formula of present value of annuity.

One of your customers is delinquent on his accounts payable balance. You've mutually agreed to a repayment schedule of $500 per month. You will charge 1.5 percent per month interest on the overdue balance. If the current balance is $18,000, how long will it take for the account to be paid off? Monthly payment Discount rate Current balance 500 1.5% 18,000 $ Complete the following analysis. Do not hard code values in your calculations. Number of months until paid off