Ten years ago, Rene bought a house at $500,000. She paid a 20% down payment and financed the rest using a 30-year fixed-rate mortgage at an APR of 4%. Today, right after her 120th mortgage payment, * Rene finds the following information from her bank's website. Loan Type Rate (APR) 15-year fixed refinance 2.8% 20-year fixed refinance 3% 7/1 ARM refinance 3% Assume all cash flows occur at month-end. APRs + nonthly compounded. a. If Rene chooses to refinance today, using a 20-year fixed refinance loan, how much can she save per month? b. Rene estimates that the total closing cost associated with refinancing to be $5,000 (including appraisal, inspection, loan application, loan origination, recording, attomey, etc). Should she refinance or not