In the TOYCO model, suppose that the changes D₁, D₂, and D3 are made simultaneously in the three operations.

(a) If the availabilities of operations 1,2, and 3 are changed to 438,500, and 410 minutes, respectively, use the simultaneous conditions to show that the current basic solution remains feasible, and determine the change in the optimal revenue by using the optimal dual prices.

(b) If the availabilities of the three operations are changed to 460,440, and 380 minutes, respectively, use the simultaneous conditions to show that the current basic solution becomes infeasible.