Please help I have tried this problem so many times and can't figure it out. Which formula do I use and would you please give a step by step guide? Thank you!

A couple plans to save for their child's college education. What principal must be deposited by the parents when their child is born in order to have $40,000 when the child reaches the age of 18? Assume the money earns 9% interest, compounded quarterly. (Round your answer to two decimal places.) $ Anion/S hummac kwm