Given:
Rodrigo puts $200.00 into an account to use for school expenses.
So, P = 200
The account earns 9% interest
so, r = 9% = 0.09
compounded annually ⇒ n = 1
We will find the balance after 4 years ⇒ t = 4
We will use the following formula:

Substitute with the given data:

Rounding to the nearest cent
so, the answer will be the balance after 4 years = $282.32