The U$.$S$.$ Department of Transportation $($DOT$)$ is planning to build a new interstate

to run from Detroit, Michigan, to Charleston, South Carolina. A number of different

routes have been proposed and are summarized in Figure $5\mathrm{.}44,$ where node $1$

represents Detroit and node $12$ represents Charleston. The numbers on the arcs

indicate the estimated construction costs of the various links $($in millions of dollars$).$

It is estimated that all of the routes will require approximately the same total driving

time to make the trip from Detroit to Charleston. Thus, the DOT is interested in

identifying the least costly alternative.a$.$ Formulate an LP model to determine the least costly construction plan.

b$.$ Use Solver to determine the optimal solution to this problem. need spreadsheet solved solution. mean spreadsheet is not clear without using vlookup i need solver solution