Bob expects to spend $150,000 every year for four years for his sons college tuition. To build up this college fund, he wants to deposit an equal amount on each of his sons 7th to 12th birthdays in a bank account earning 12% per annum compounded quarterly. What uniform annual amount should he deposit, if he plans to withdraw $150,000 on each of his sons 17th to 20th birthdays? Assume that the last withdrawal closes the account.