Problem 15. James repays a loan of 10,000 by establishing a sinking fund and making 20 equal payments at the end of each year. The sinking fund earns 7% effective annually. Immediately after the fifth payment, the yield on the sinking fund increases to 8% effective annually. At that time Joe adjusts his sinking fund payment to S so that the sinking fund will accumulate to 10,000 20 years after the original loan date. Determine S