=2.22. You are given the following linear programming model in algebraic form, with x1 and x2 as the decision variables:

Minimize Cost = 40x1 + 50x2 subject to Constraint 1: 2x1 + 3x2 ≥ 30 Constraint 2: x1 + x2 ≥ 12 Constraint 3: 2x1 + x2 ≥ 20 and x1 ≥ 0 x2 ≥ 0

a. Use the graphical method to solve this model.

b. How does the optimal solution change if the objective function is changed to Cost = 40x1 + 70x2?

c. How does the optimal solution change if the third functional constraint is changed to 2x1 + x2 ≥ 15?