4. A real estate company is considering five possible projects: a small condominium complex, a small shopping center, a warehouse, a small business office building and a sports arena. Each of these projects requires different funding over the next three years, and the net present values of the projects also varies. The following table provides the required investment amounts (in $10,000s) and the net present value, NPV (in $10,000s), of each project: 1 NPV 300 290 PROJECT Condominium Shopping center Warehouse Business Office Building Sports Arena 250 YEAR 1 YEAR 2 YEAR 3 64 60 58 50 45 58 50 32 60 55 45 38 50 44 40 240 275 The company has $2,500,000 to invest in year 1, $1,850,000 to invest in year 2 and $2,300,000 in year 3. The company wants to select at least 3 projects. In addition, the company also wants to select at least one project from the shopping center and sports arena projects. a. Formulate an integer optimization model for this problem to maximize the total NPV in this situation by defining the decision variables, the objective function and all the constraints. What type of integer optimization model is this? Briefly describe what the objective function and each constraint represent. b. The optimal solution for the above problem is given below. Variable values are X1 = 1, X2 = 1, X3 = 1, X4 = 0, X5 = 1 Objective function value is 1115 Interpret the optimal solution to make a recommendation to the company