John is planning to retire in 15 years. Money can be deposited at 8% compounded quarterly. What quarterly amount must be deposited at the end of each quarter until John retires so that he can make a withdrawal of $ 20,413 semiannually over the first 5 years of his retirement. Assume that John's first withdrawal occurs at the end of six months after his retirement. (Do not use the $ sign in your answer and round it to 2 decimal points)