A $150bicyclewaspurchasedon December 1with a $15 down payment. The balance is to be paid at the rate

Question:

A $150bicyclewaspurchasedon December 1with a $15 down payment. The balance is to be paid at the rate of $10 at the end of each month, with the first payment due on December 31. The last payment may be some amount less than $10. If interest on the unpaid balance is computed at 11/2%per month, how many payments will there be, and what is the amount of the final payment?