12) Linear mathematical programming techniques assume that all parameters in the models are known with 13) A variable measure how much or how many items to produce, purchase, hire, etc. 14) The property of linear programming models indicates that the rate of change or slope of the objective function or a constraint is constant. 15) The property of linear programming models indicates that the values of all the model parameters are known and are assumed to be constant. 16) The region that satisfies all of the constraints in a graphical linear programming problem is called the solution area. 17) In the formulation of a constraint a variable is subtracted. 18) An infeasible solution does not at least one of the constraints. 19) The optimal solution to a linear programming model that has been solved using the graphical approach is typically at some of the feasible region. 20) A management science technique that does not assume that all parameters are known with certainty is a(n) technique