5. (20 marks) Before doing this problem, look at the Steiner tree Wikipedia article, found here. See the picture of the four point solution. A mining company has four mines located only a few kilometres apart. At 500 metres below the surface of the earth, they wish to build a tunnel system to connect these four mines. The most convenient points for these connections are at reference points (100,2300),(300,400),(3700,1800), and (4100,600), where (a,b) is a metres east and b metres north of a common reference point. The company wishes to determine where the connecting tunnels should be made. For your own benefit, plot the four points on a piece of graph paper. Using the information from the Wikipedia article, there are two ways to draw the Steiner tree, but one is much better than the other. Determine how you would connect these four points. (You do not need to submit this part.) (a) Give the algebraic model in LINGO or an Excel file. (b) Solve this model using LINGO or the Excel Solver. (c) State the solution in words