In order to determine the interest earnt after 5 years, use the following formula for the simple interest:
I = P·r·t
where
P: prinpal investment = $600
r: annual interest rate = 2.5% = 0.025
t: time = 5 years
replace the previous values of the parameters into the formula for I:
I = ($600)(0.025)(5)
I = $75
Hence, the account will have an interest of $75 after 5 years