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$)![$Hint: Add two

new binary variables to the previous model$]$

Binary$/$Integer Constraints Not Working: Solver $->$ Options $->$ All Methods $->$ Uncheck $$Ignore Integer$$

Having made any revisions necessary, use the LP solver to determine what network segments should

be improved to efficiently transmit the peak requirement of $35$ GB$/$s from A to G at the lowest possible

cost$.$ Please note that the IF function in Excel is not linear. $[$Hint: You need to add five constraints using the

$9999$ trick to formulate the new router upgrade policy for nodes C and F$.$ The updated optimal objective is

$$38\mathrm{.}0$ M$.]$