A loan of L is repaid with a payment made at the end of each year for 20 years. The payments are 100, 200, 300, 400, and 500 in years 1 through 5, respectively. In the subsequent 15 years, equal annual payments of 600 are made to pay off the loan. The annual effective interest rate is 5%. Find the outstanding loan balance at the end year 4 (after repayment) using the prospective approach the retrospective approach