3) A factory produces four products. Each product needs to be processed successively on two machines - machine A and then machine B. The processing times in hours per unit of the products on the two machines are shown in the following table. Processing time (hours) per unit of Machine A Product 1 Product 2 Product 3 Product 4 B 2 3 3 4 2 2 1 2 The total cost of producing one unit of each product is based directly on the machine time. Assume that the costs per hour for machines A and B are $10 and $5, respectively. The total number of hours available each month is 500 for machine A and 380 for machine B. The unit sales prices for products 1, 2, 3, and 4 are $65, $70, $55, and $45, respectively. The factory wants to determine the monthly production quantity of each product so that the total profit can be maximized. Formulate the problem as a linear programming model and solve it using Excel solver. (10 points)