A couple who borrow $80,000 for 30 years at 8.4%, compounded monthly, must make monthly payments of $609.47. (a) Find their unpaid balance after 1 year. (Round your answers to the nearest cent.) (b) During that first year, how much do they pay towards the principle? (Round your answer to the nearest cent.) During that first year, what are their total payments? (Round your answer to the nearest cent.) $ During that first year, how much interest do they pay? (Round your answer to the nearest cent.) $