Can you guys help me with this question? I';m so confused on how I should approach it:

Tom’s father paid $500 into an account on the day Tom was born. ?After that, he paid $500 into the account on Tom’s bday until Tom’s 18th bday. ?If the account accrued interest at 8%p.a compounded monthly, calculate how much Tom would receive on his 18th bday.

A: 20880.97

Thanks in advance!