Below is the linear programming for the Shortest Path Problem.

Considering the first contraint in the mathematical model :

=1=

What is the logic behind this contrain?

A) To make sure there is only one solution

B) To make sure there is only one path out of starting node(source node)

C) To make sure the variable stays binary

D) This contraint is redundant and not necessary

Minimize: 2.2CX Subject to: 2x=1 Vjes 2,4,-2.x, =0 V j #s, j#t { x=1 vj=t x. 20 where: x = Number of units flowing from node i to nodej ci = Cost per unit for flow from node i to node i S = Source node - where flow starts t = Terminal node - where flow ends