What formula do I use for this question?

Now take the amount of your answer in Ques 5a, and assume this money is invested in an annuity due with the first payment made at the beginning of the 6th year. The annuity due makes a total of 15 yearly (equal) payments. How much will the annual payments be from years 6 to 20, if the rate at which these payments are discounted is also 3.5 percent?