You plan to purchase a $340,000 house using either a 25-year mortgage obtained from your local savings bank with a rate of 8.10 percent, or a 10-year mortgage with a rate of 7.10 percent. You will make a down payment of 20 percent of the purchase price. a. Calculate the amount of interest and, separately, principal paid on each mortgage. What is the difference in interest paid?
b. Calculate your monthly payments on the two mortgages. What is the difference in the monthly payment on the two mortgages?

a. Interest under 10 year mortgage = CUMIPMT(7.1%/12, 10*12, 340000*80%, 1, 10*12, 0)

Interest under 10 year mortgage = 108662.44

Interest under 25 year mortgage= CUMIPMT(8.1%/12, 10*12, 340000*80%, 1, 25*12, 0)

Interest under 25 year mortgage= 363217.16

Difference in interest = 363217.16 - 108662.44

Difference in interest = 254554.72

b. Monthly payment under 10 year = PMT(7.1%/12, 10*12, 340000*80%)

Monthly payment under 10 year = 3172.19

Monthly payment under 25 year = PMT(8.1%/12, 25*12, 340000*80%)

Monthly payment under 25 year = 2117.39

Difference in the monthly payment = 3172.19 - 2117.39

Difference in the monthly payment = 1054.80