Amelia takes out a loan for $18,000 at a nominal interest rate of 7.2% compounded quarterly. She'll repay the loan with level payments at the end of each quarter for the next 10 years (except for a possibly slightly reduced final payment).

a) Find the amount of the regular quarterly payments and the amount of the final quarterly payment.

b) Amelia hits a financial set-back and can't make the 15th payment, but makes all the other payments as scheduled. She still wants to finish paying the loan at the end of the 10 year period. What should her final payment be to settle her debt ?