please explain and show work to help me through the question

9. Refinancing. Doug and Lynn bought their home three years ago. They have a mortgage payment of $601.69. Interest rates have recently fallen, and they can lower their mortgage payments to $491.31 if they refinance. What would their annual savings be if they refinance? They are in a 12% marginal tax rate bracket and have sufficient deductions to itemize. (Hint: Consider the reduc- tion in tax savings.)