Repayments at $1280 per month over 5 years = 1280 x 12 x 5 = $76,800
Adding in the deposit of $7,500, total repaid = $76,800 + $7,500 = $84,300
So, total cost is $84,300 over 5 years to buy a car valued at $42,000, thus paying interest of $84,300 - $42,000 = $42,300
This is what is known as a shitty deal... for the customer, though awesome for the finance company. Simple interest, this is at least 20% pa.