Alaskan Railroad is an independent, stand-alone railroad operation not connected to any other rail service in North America. As a result, rail shipments between Alaska and the rest of North America must be shipped by truck for thousands of miles or loaded onto ocean-going cargo vessels and transported by sea. Alaskan Railroad recently began talks with the nation of Canada about expanding its railroad lines to connect with the North American railway system. The North American railroad system currently provides service to New Hazelton and Chetwynd. Alaskan Railroad would like to expand its railway so as to be able to reach at least one of these cities from both Skagway and Fairbanks. Figure 7.19 summarizes the various rail segments that could be built. Of course, there is a financial cost associated with building each potential rail segment, and the company would like to minimize those costs. However, environmental costs are also associated with constructing each rail segment. It is difficult to quantify these costs financially, but the company commissioned a study in which ecological experts assessed the environmental impact of building each rail segment and summarized their findings on a scale of 0 to 100 (where 0 represents the lowest negative impact, and 100 represents the highest negative impact). The financial cost and environmental impact score for each potential rail segment are shown on the arcs in Figure 7.19.

a. Implement a network flow model for this problem, and determine the least expensive way to connect the cities of Skagway and Fairbanks to the North American rail system. What is the financial cost of this route, and what is its total environmental impact score?
b. Now determine the solution for connecting the cities of Skagway and Fairbanks to the North American rail system in a manner that minimizes the total environmental impact. What is the financial cost of this route, and what is its total environmental impact score?
c. Suppose Alaskan Railroad considers minimizing environmental impact to be equally important as minimizing financial cost for the new rail lines. What solution does this suggest? At this solution, how far (on a percentage basis) is each objective from its best possible value?

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33.8 75 20.0 10.0 84 Tok2 5 Camacks $19.6 20.1 39 S37.4 49 $25.6 70 $14.4 86 Boya Lake $ Whitehorse4 Watson Lake S10.3 S21.7 76 S20.1 7 Fort Nelson $31.0 24.7 35 81 38.8 S6.6 86 24.9 51 New Hazelton9 10 Chetwynd