The additional concern not considered in the previous tutorial is that the routers at nodes C and F are

each almost maxed out. If in $$Part b$$ any additional capacity is built $$into$$ or $$out of$$ node C $($or

similarly at node F$),$ then the router at that station MUST be upgraded. This upgrade would cost a fixed

amount of $$2$ million at node C or a fixed amount of $$3$ million at node F or even at both, which requires

you to revisit the objective cell $($Expansion Costs of Links $+$ Upgrading Costs of Nodes$)!$