factory organization course exam

Mr. M wants to buy an X car from a dealership. The gallery presented 2 payment plans to Mr M. regarding the payment of the price of the car. According to the first plan, the cash price of the car is 30,000 TL. According to the second payment plan, 10.000 TL in advance and 1.500 TL equal installments at the end of each month for 24 months. Accordingly, what is the interest rate applied by the gallery for deferred payments