A to Z Mortgage made a home equity loan to your friend. For a 4-year loan of $10,000 at 10% per year, what annual payment must he make to pay off the entire loan in 4 years if interest is charged on (a) the original principal amount of $10,000, and (b) the unrecovered balance? (c) What is the difference in the annual payments between the two bases for interest? Which method requires more money to repay the loan?