In Section 4.5.1 we studied Dijkstra's link-state routing algorithm for computing the unicast paths that are individually the least-cost paths from the source to all destinations . The union of these paths might be thought of as forming a least-unicast-cost ,path tree (or a shortest unicast path tree, if all link costs are identical). By constructing a counterexample, show that the least-cost path tree is not always the same as a minimum spanning tree.