13. John borrows X and repays the principal by making 10 annual payments at the end of each year into a sinking fund which earns an annual effective rate of 8%. The interest earned on the sinking fund is the 3rd year is 85.57. Calculate X. 14. Jon has borrowed $50,000 on which he is paying interest at 17.5% effective per year. He is contributing a constant amount P to a sinking fund at the end of each year. The sinking fund earns an annual effective rate of 9%. His combined payment to both the fund and the loan is $9,116.82 annually. Determine the year in which the balance of the sinking fund will be sufficient to repay the loan. 15. A Loan is amortized over five years with monthly payments at a nominal interest rate of 9% compounded monthly. The first payment is 1000 and is to be paid one month from the date of the loan. Each succeeding monthly payment will be 2% lower than the prior payment. Calculate the outstanding loan balance immediately after the 40"payment is made