During four years of college, Nolan MacGregor's student loans are $4000, $3500, $4400, and $5000 for freshman year through senior year, respectively. Each loan amount gathers interest of 1.2%, compounded quarterly, while Nolan is in school and 3.6%, compounded quarterly, during a 6-month grace period after graduation.

(a) What is the loan balance after the grace period? Assume the freshman year loan earns 1.2% interest for 3/4 year during the first year, then for 3 full years until graduation. Make similar assumptions for the loans for the other years. (Round your answer to the nearest cent.) $  

(b) After the grace period, the loan is amortized over the next 10 years at 3.6%, compounded quarterly. Find the quarterly payment. (Round your answer to the nearest cent.) $  

(c) If Nolan decides to pay an additional $90 per payment, how many payments will amortize the debt? (Round your answer up to the next whole number.) quarters

(d) How much will Nolan save by paying the extra $90 with the number of payments from part (c)? (Round your answer to the nearest cent.) $