What formula should I use ro get this answer?

Cindy just had a baby and wants to start saving for the baby's college education. Her goal is to save a constant amount every year for 17 years (starting at the end of this current year), so that she will be able to withdraw $25,000 a year, for 4 years, starting at the end of year 18. How much will she need to save per year for the first 17 years in order to achieve her goal? Assume she can earn an annual interest rate of 5%. $3,431 $5,882 $5,556 $2,487