Daniels bought a car from Caddy Cadillac Co. because his credit rating was poor, he had his brother act as surety for the loan to purchase the car. His brother signed the purchase contract on the line marked "buyer" and he signed on the line marked "co-buyer." The contract was assigned to GMAC. When a default occurred, GMAC repossessed the car, found it was a total loss and sued both brothers. However, they couldn't find Daniels, so they sued the brother who was the surety. The brother argued that he was a guarantor only, and thus, the bank first would have to proceed against his brother before it could proceed against him. GMAC argued that as the brother had signed the contract as a buyer, he was not a guarantor but a surety, and thus, the bank could proceed against him directly. Who is correct and why?