10. Maximal/minimal flow in networks with lower bounds. The maximal flow algorithm given in this section assumes that all the arcs have zero lower bounds .In some models,the lower bounds may be strictly positive ,and we may be interested in finding the maximal or minimal flow in the network (see case 6-3 in Appendix E). The presence of the lower bound poses difficulty because the network may not have a feasible flow at all. The objective of this exercise is to show that any maximal flow model with positive lower bounds can be solved using two steps.