13.(10pts) A couple borrows$300,000 at an APR of 4.8%compounded monthly. They have a 30-year mortgage with monthly payments of $1,574.

(a) Find the total interest paid if they pay off the loan on schedule as described above.

(b) 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 $3,000. Find the new monthly payment.

(c) Find the amount saved by refinancing.