how is this calculated?

Mr. and Mrs. Houghton want to set up an account that will generate sufficient interest on retirement to generate $1200 to meet their basic living expenses. a.) Find the future amount necessary that will generate $1200 per month interest if they can get 5.15% interest compounded monthly on those monies. ROOSIS 12 VES T? 279,611.65 b.) Find the monthly payment they would have to make into an ordinary annuity to obtain the future value found in part a) if their annuity money earns 7.65% monthly compound interest and the term is 25 years. 1 311.14