Consider a capital budgeting example with five projects from which to select. Let x1 = 1 if project a is selected, 0 if not, for a = 1, 2, 3, 4, 5. Projects cost $100, $200, $150, $75, and $300, respectively. The budget is $450.
Write the appropriate constraint for the following condition: If project 3 is chosen, project 4 must be chosen.