I open an account the day my son is born. I want to deposit the same amount every year, from the day he's born up to and including his 18th birthday. I would like this to be able to support his post-secondary education which I expect to cost $20,000 on his 18th birthday, and every birthday thereafter until 22nd birthday because of the higher tuition. So, he will need $20k per year up to and including his 21st birthday, and then $30k per year after that, up to and including his 26th birthday. How much will I need to deposit every year so there's enough in the account to support his education?

The interest rate is 9% by the way. Please explain how to approach this question