Answer: Interest rate =16%

Working noted for the above answer is as under

We have been provided with the information as

$2,500 loan taken next year

when $4,500 must be repaid in year 5

The formula for interest rate from Present Value and Futur Value are as under

Interest rate =        (FV/PV- 1)  / t

Now we put the figures in to the formula as under

Interest rate =        (4500/2500- 1)  /5 years

solving this equation we will get

Interest rate =16%