Solve the following problems using graphical linear programming. Use simultaneous equations to determine the optimal values of the decision variables. Answer the following (4) questions for each model (both parts a and b): 1) What are the optimal values of the decision variables and Z? 2) Do any constraints have nonzero slack? If yes, which one(s) and how much? 3) Do any constraints have nonzero surplus? If yes, which one(s) and how much? 4) Are any constraints redundant? If so, which ones? Explain briefly a. Minimize Z = 2x + 3y Subject to 4x + 2y = 20 2x + y 2 18 x + 2y = 12 X, y 20 b. Minimize Z = 1.85 + 2.2T Subject to 5S + ST 2 200 grams 15S + 6T 2 240 grams 4S + 12T 2 180 grams T 10 grams ST20