Question: Solve the linear programming model formulated in Problem 14 for United Aluminum Company graphically.

a. How much extra (i.e., surplus) high-, medium-, and low-grade aluminum does them company produce at the optimal solution?

b. What would be the effect on the optimal solution if the cost of operating mill 1 increased from $6,000 to $7,500 per day?

c. What would be the effect on the optimal solution if the company could supply only 10 tons of high-grade aluminum?