8. John deposits 100 at the end of each year for twenty years into a fund earning an annual effective interest rate of 7%. Mary makes twenty deposits into a fund at the end of each year for twenty years. The first ten deposits are 100 each, while the last ten deposits are 100 + X each. The fund earns an annual effective interest rate of 8% during the first ten years and 6% annual effective interest thereafter. At the end of twenty years, the amount in John's fund equals the amount in Mary's fund. Calculate X