1) One of your customers has a current balance of $18,000 in his accounts payable balance. You will charge a 15.6 percent interest compounded monthly on the overdue balance if the customer agrees to a repayment balance schedule of $450 per month. How long will it take for the account to be paid off?

a) 56.8 months

b) 56.8 years

c) 13.7 months

d) 13.7 years