更新1:
A takes out a 21-year mortgage of 250000 dollars for his new house. A gets an interest rate of 13.2%(p.a.)compounded monthly. He makes equal monthly payments, the first coming in one month. After making the 64th payment, A wants to refinance his house to reduce his monthly payment by 400 dollars, and he gets a new interest rate(7.2%p.a.compounded monthly)He then makes new equal monthly payments for as long as necessary, followed by a single smaller payment. What is A's final loan payment?
更新2:
Since there is a word limit,I simplify the question above.
