Can you please show calculations instead of Excel version. I've been trying to figure out what it is I'm missing. Thanks.

You're purchasing an automobile that costs $25,000. The dealership offers you either a $1,000 rebate applied toward the purchase price, or 3.9% financing for 60 months with the payments done at the end of each month. You're also pre-approved for an auto loan through the local credit union at an interest rate of 7.5% for 60 months. Should you take the $1,000 rebate and finance through the credit union or forgo the rebate and finance through the dealership at the lower 3.9% APR?

Can you please show calculations instead of Excel version. I've been trying to figure out what it is I'm missing. Thanks.