4 Two types of resources, X and Y, are used to build a profit-making certain civil engineering facility. Due to inflation and uncertainty of supply, their unit prices change with time. When the unit price of Y is $7 million and the unit price of X is $6 million, the total cost must not exceed 42 million dollars. When the unit price of Y is $3million and the unit price of X is $8 million, the total cost must not exceed 24 million dollars. The amount of Y used must not exceed the number of X used less 2. Also, X and Y cannot be negative. From experience, it has been found that the overall revenue W, is given by the function 3X + 10Y. It is sought to maximize the revenue. (a) Write the objective function and the constraints. (b) Solve the optimization problem using a sketch (graphical method) Solve this problem manually