A company manufacturing two products X and Y by using two machines A and B. Machine A has 4 hours of capacity available during coming week. Similarity, the available capacity of machine B is 24 hours during the coming week. One unit of product X requires one hour of machine A and 3 hours of machine B. Similarity, one unit of product Y requires 1 hour of machine A and 8 hours of machine B. When one unit of X is sold in the market, it yields a profit of $5 per product and that of Y is $7 per unit. Solve the problem by using graphical method to find the optimal product mix to maximize the profit.