[Chapter 12] Integer Linear Optimization Models The Highland Investment Group is considering investing in four projects. The expected net present value (NPV) and the required capital at the present time for each project are given in the table below. Project Expected NPV ($) Required Capital ($) 1 10,000 3,000 2 16,000 5,000 3 6,000 2,000 4. 9,000 4,000 At present, a budget of $12,000 is available for investment. Highland has specific requirements for the investment, as detailed in the Constraints section given below. Please help Highland develop an investment plan by formulating an integer linear optimization model Write your final answer only (without intermediate steps) for the fill-in-the-blank questions, 1. Define the decision variables. At least two projects must be selected. Oxq + X2 + X3+ X452 OX1 + X2+ X3 + X4 2 X1 + X2 + X3 + X4 = 2 OX1 + X2 + X3 + X4 2 2 Question 21 (3 points) Constraints on decision variables. OX1 + X2 + X2 + X4 2 1 X1, X2, X3, X4 = 0 or 1 X.. X. X. X. 20