Cindy just bought a house for $425,000 with a 15% down payment. She plans to pay it off with a 25 year mortgage making monthly payments at a rate of 6.8%.\ a .How much interest will she have paid after five years?\ b. If she refinances at 6.2% what are her new payments?\ c. Assuming she wishes to make additional payments of $1,800 every four months for the first three years and then $2,500 every eight months for the following two years how does this change your answer to parts a and b?