A car manufacturer makes two versions of the same car, a regular model and a premium model. They make x1 regular models per day and x2 premium models per day. The profit per regular model is $5000 and the profit per premium model is $8500 (x1 and x2 are unknown values both greater than or equal to 0). The daily demand for these cars is limited to and most 8 regular models and 6 premium models. In addition, the manufacturer can make a maximum of 12 cars of either type per day. How many cars of each model should the manufacturer make in order to maximize profit?