7. In the transshipment model of Example 5.5-1, define Xij as the amount shipped from node i to node j. The problem can be formulated as a linear program in which each node produces a constraint equation. Develop the linear program, and show that the resulting formulation has the characteristic that the constraint coefficients, aij, of the variable Xij are

{

I, in constraint i aij = -1, in constraint j 0, otherwise