solve without excel

Roy borrows $25,000 at an effective annual interest rate of 12%. He has the following options for repayment: (c) Annual amortization method, with payments made at year-end for 10 years. Paying annual interest at year-end and building up a sinking fund (earning effective annual interest rate of 7%), by making level annual payments at year-end, to pay off the loan at the end of 10 years. Determine the absolute value of the difference between the total annual payment under option 1 and the total annual payment under option 2. (7 marks) A loan is being repaid by 15 annual installments of 1,000 each. Interest is at an effective annual rate of 5%. Immediately after the fifth installment is paid, the loan is renegotiated. The revised amortization schedule calls for a sixth installment of 700, a seventh installment of (700+X), with each subsequent installment increasing by X over previous payment. The period of the loan is not changed. Determined the revised amount of the last installment. (d) (8 marks) Total : 25 marks]