We receive a mortgage loan of $200,000 for 20 years.. The mortgage rate is 12% per annum. First, derive the monthly payment we ought to make to the bank to amortize the loan. Secondly, compute the remaining amount we still owe the bank, if we pay an additional single sum of $40,000 after 4years. Thirdly, as part of this computation find how many more months, we will pay the bank to induce the loan expire. Fourthly, if we accumulate a lot by year 10(end of the year), how much would we give additionally to the lender to eliminate the loan?