The following questions refer to a capital budgeting problem with six projects represented by 0 - 1 variables x2,x2,x3,x4,x5, and x4 - (a) Write a constraint modeling a situation in which exactly three of the projects 1,3,5, and 6 must be undertoken. (b) Write a constraint modeling a situation in which, if projects 3 or 5 must be undertaken, then they must be undertaken simultaneously. x3x5=0 (c) Write a constraint modeling a situation in which project 1 or 4 must be undertaken, but not both. X2+X4=1 (d) Write constraints modeling a situation where project 4 cannot be undertaken uniess projects 1 and 3 also are undertaken. (Enter your antwer as a comina sepurated lis and/or inequalities.) (e) In addition to the requirement in part (d), assume that when projects 1 and 3 are undertaken, project 4 also must be undertakea, (Enter your answer as a comma--epet equations and/or inequalitiesi.)