3. The network in Figure 5.10 shows the routes for shipping cars from three plants (nodes 1, 2, and 3) to three dealers (nodes 6 to 8) by way of two distribution centers (nodes 4 and 5). The shipping costs per car (in $100) are shown on the arcs.

(a) Solve the problem as a transshipment model.

(b) Find the new optimum solution assuming that distribution center 4 can sell 240 cars directly to customers.