Question: The following questions refer to a capital budgeting problem with six projects represented by binary variables _α1, _α2, _α3, _α4, _α5, and _α6.

a. Write a constraint modeling a situation in which two of the projects 1, 3, 5, and 6 must be undertaken.

b. Write a constraint modeling a situation in which, if project 3 or 5 is undertaken, they must both be undertaken.

c. Write a constraint modeling a situation in which project 1 or 4 must be undertaken, but not both.

d. Write constraints modeling a situation where project 4 cannot be undertaken unless projects 1 and 3 also are undertaken.

e. Revise the requirement in part d to accommodate the case in which, when projects 1 and 3 are undertaken, project 4 also must be undertaken.