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Consider the following network. The net difference for each node is presented next to each node. The arcs are uncapacitated $($i$.$e$.,$ you can send as much flow on them as you$$d like$),$ and the unit cost of shipping on each arc is $1.$

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$($a$)$ Report the transshipment node, and briefly describe its purpose.

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$($b$)$ Formulate this as a minimum cost flow problem. Don$$t solve.

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Next, consider a new case where node E has received $20$ units of product. Its net difference is now $20.$

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$($c$)$ Re$-$draw the network with the new condition. Include any updates that you would need to prepare it be formulated as a minimum cost flow problem, though don$$t formulate the problem itself.