Solve the linear programming model formulated in Problem 52 for Exeter Mines by using the computer.

a. Do any of the mines have slack capacity? If yes, which one(s)?

b. If Exeter Mines could increase production capacity at any one of its mines, which should it be? Why?

c. If Exeter decided to increase capacity at the mine identified in (b), how much could it increase capacity before the optimal solution point (i.e., the optimal set of variables) would change?

d. If Exeter determined that it could increase production capacity at mine 1 from 350 tons to 500 tons, at an increase in production costs to $43 per ton, should it do so?