### Problem R5.4

Give an example of an undirected, weighted graph for which there is a pair
of vertices `s` and `t` where the shortest
path from `s` to `t` does
not lie within the graph's minimum spanning tree. Justify your
answer.

In the above graph, there is just one minimum spanning tree,
which includes the edges labeled 2 and 3. However, the shortest
path from `s` to `t` is to take
the edge of length 4, which is not included
in the minimum spanning tree.