I don't get it

Part 3: Interest Find the amount of interest you will be charged for the month for each of the following. We will assume this is a 30 day month. 7. The annual interest rate is 20%. The balance after the grace period was $15,000. A payment of $2,500 was made on the 3" day. What is the interest for the month? C $ 4 6 V Po 8 9 t y u g h Lo K