Create an LP model that will find the shortest route distance from node A to node G.

**Let Xij equal to 1 if the arc from i to j is on the shortest path and 0 otherwise (I and j can be A, B, C, D, E, F, or G)**

A. Write the flow balancing constraint for node D (include all directional arcs)

B. If the optimal solution is: Xab = 1, Xce = 1, Xeg = 1, and all other variables equal to 0, what is the length of the shortest path from Node A to node G?

C. Consider the following additional requirement regarding the path including the arc from B to C and the arc from C to F: the path should either include both arcs or non but it cannot include oboe one of the two:

Either (Xbc=1 and Xcf=1) or (Xbc=0 and Xcf=0); cannot have one equal 0 and the other equal 1. Write a constraint to represent the above requirement.

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