Formulate each of the following requirements as integer linear programming constraints. a) (5 points) Let x represent a decision variable which can only take values 100, 118, and 155. b) (5 points) Let x represent the number of cars produced in a month. Either x is between 10 and 20 or it is between 30 and 50. c) (5 points) Let x be an integer variable that can take values between 0 and 50 and z be an integer variable that can take values between 0 and 20. If x is at least 15, then z should be at most 5.