How many times have I said this? You MUST learn to use Basic Principles. Draw a map and reason it out.
i = 3.5% = 0.035
<== Monthly interest rate.
Note: I'll just use 'i' in order to make the notation more convenient. Just remember this is the MONTHLY rates of interest.
t = time in years
t = 0 ==> 600.00 <== There's the loan.
<== There's the value after two years (24 months).
Pull your Annuity Immediate formula out of your hat...(or learn to derive it!)
P = Equal Monthly Payment
Note: Remember, this is a monthly rate. 'v' is the MONTHLY rate of discount.
Solve for 'P' and you nearly are done.