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13. (12 pts) A couple borrows $300,000 at an APR of 4.8% compounded monthly on a 30-year mortgage with monthly payments of $1,574. (a) How much of the first payment goes to interest? (b) Find the total interest paid over the life of the loan. (c) After making their 70th payment, they refinance the loan at an APR of 3.6% compounded monthly for 15 years. The refinanced amount includes the unpaid balance from the original loan plus a refinance charge of $2,000. Find the new monthly payment. (d) Find the amount saved by refinancing