onsider the following transshipment network for finding the shortest route from node $1$ to node $7.$

$($a$)$ Formulate a linear programming model of the problem. $($Express your answers using $x_{ij},$ where each $x_{ij}$ is either $0$ or $1$ for the arc from node to node $j.)$

Min

s$.$t$.$

Node $1$ Flows