George plans to start depositing money into an account five years from now. The first deposit amount is $1000 and this value increases by $100 every vear thereafter. The final deposit into the stated account is going to occur at the end of year 15. He then will withdraw four equal values of K from his account in years 18 through 21 in order to pay for his son's college education. What is the value of K that makes the aforementioned withdrawal equivalent to those deposits, knowing that the rate of return on the account is 6% per year, compounded quarterly