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% per month interest on the overdue balance. If the current balance is $18,000.00, it will take _____________ months for the account to be paid off?

Monthly Payment: 500

Discount rate: 1.5%

Current Balance: 18000

*please show using excel to solve* Thanks!