Question 17
A toy factory has 2 machines: machine A produces 12 teddy bears/hour with a cost of 240,000 VND/hour, and machine B produces 8 cars/hour with a cost of 200,000 VND/hour. A production order requires at least 60 teddy bears and at least 40 cars. Due to labor limitations, the total operating time of both machines must not exceed 10 hours. Find the operating time for each machine $(x,y)$ to minimize the cost. Calculate that optimal cost.