The company has many other planes that fly at different schedules each night, so the potential cost savings from efficient fuel purchasing is quite significant. But before turning you loose on all of their flight schedules, the company wants you to create a spreadsheet model to determine the most economical fuel purchasing plan for the previous schedule. $($Hint: Keep in mind that the most fuel you would purchase at any departure point is the maximum allowable fuel level for takeoff at that point. Also, assume that whatever fuel is on board when the plane returns to Atlanta at the end of the rotation will still be on board when the plane leaves Atlanta the next evening.$)$

Draw the network diagram for this problem.

Implement the model for this problem in your spreadsheet and solve it$.$

How much fuel should US Express purchase at each departure point and what is the cost of this purchasing plan?