The optimal solution to the original Grand Prix problem indicates that with a unit shipping cost of $180, the route from plant 3 to region 4 is evidently too expensive, as no autos are shipped along this route. Using the file P14_14.xlsx, calculate how much this unit shipping cost would have to be reduced (to the nearest dollar) before some autos are shipped along this route?

Input Data for Grand Prix
		To
		Region 1	Region 2	Region 3	Region 4	Capacity
From	Plant 1	$131	$218	$266	$120	450
	Plant 2	$250	$116	$263	$278	600
	Plant 3	$178	$132	$122	$180	500
	Demand	450	200	300	300