Before doing this problem, look at the Steiner tree Wikipedia article - https://en.wikipedia.org/wiki/Steiner_tree_problem. 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.

(a) Give the algebraic model of this problem. (b) Solve this model using Excel Solver. (c) State the solution in words.