On the day his son was born, a father decided to establish a fund for his son's college education. The father wants the son to be able to withdraw $4000 from the fund on his 18th birthday, again on his 19th birthday , again on his 20th birthday ,and again on 21st birthday. If the fund earns interest at 8.5% per year ,compounded annually ,how much should the father deposit at the end of each year, up through the 17th year