A 20-year loan of $100,000 is to be repaid with payments at the end of each year. Each payment is split between interest and a sinking fund deposit. Interest on the loan charged at 8% annual effective rate. The annual effective interest rate earned by is the sinking fund is 6% However, beginning in the 12-th year, the annual effective interest rate on the sinking fund drops to 4%. As a result, the annual payment to the sinking fund is then increased by X. Find X.