The maximum flow problem is again structured on a network;
but here the arc capacities, or upper bounds, are the only
relevant parameters. The problem is to find the maximum
flow possible from some given source node to a given sink
node. A network model is in Fig. 17. All arc costs are zero,
but the cost on the arc leaving the sink is set to -1. Since
the goal of the optimization is to minimize cost, the maximum
flow possible is delivered to the sink node.