Consider a problem with two nodes, 1 and 2, and two arcs (1, 2) and (2, 1). The node supplies are s1 = s2 = 0. The problem is
![](https://test.transtutors.com/qimg/54fb88c7-b7fe-4f24-8825-48087da492a8.png)
![](https://test.transtutors.com/qimg/41001743-2ebe-4af7-b2eb-423e95b4b99e.png)
Calculate the dual function and verify that the optimal primal and dual costs are both equal to -∞, consistently with Prop. 9.4.