(5) [BA || Plus calculator desirable] Sean and Karl each borrowed an identical amount from their parents at an annual effective rate of interest of 5%. Sean repays his loan by making monthly payments at the end of each month for eight years. For the rst four years these monthly payments are each $200 and for the next four years they are each $500. Karl makes payments of $7,000 at times T, 2T, and 3T, $3,000 at times 4T and 5 T, and a payment of $2,000 at