A $140 000 mortgage is to be repaid over a 15-year period by monthly payments rounded up

Question:

A $140 000 mortgage is to be repaid over a 15-year period by monthly payments rounded up to the next-higher $50. Interest is 4.35% compounded semi-annually.
(a) Determine the number of rounded payments required to repay the mortgage.
(b) Determine the size of the last payment.
(c) Calculate the amount of interest saved by rounding the payments up to the next-higher $50.