**
Homework 9: Due 11/8
**

Compute a *minimum spanning tree* of the edge-weighted
graph defined by the cities
and edges in miles.dat.
This graph consists of 128 vertices, each vertex corresponding to a city,
and edges connecting all pairs of vertices.
The weights of these edges are the mileage distances between pairs of cities
given in miles.dat.
Use Prim's algorithm (as described in Project 2)
to compute the minimum spanning tree.

Submit a program called `MST.java` containing your solution.
The program should start by reading from miles.dat;
feel free to use code from City.java to do this.
The output should consist of all the edges in the computed miniumum spanning
tree.