please solve this problem without using Excel and show all steps.

Todd has a $100,000 25-year mortgage with a 12% nominal interest rate convertible monthly. The first payment is due one month after the mortgage is taken out. Twelve years after taking out the mortgage (after making his 144th payment), he refinances with a new nominal interest rate of 8%, again convertible monthly. The new mortgage will be paid off on the same date as the original one. Calculate the difference in the monthly mortgage payment after refinancing. (CAS 11/93 #7]