Consider the following breadth-first search algorithm: bfs(s) mark s as visited create empty queueq g.engueue(s), s.distance while ( ! q . isEmpty()) { = e q.dequeue(v) for each unvisited vertex u adjacent to v [ mark u as visited q.engueue(u), u.distance v.distance 1 This algorithm can be applied to an undirected graph G (V,E) with some given vertex s Show that the following condition 13: if the vertices of q are are denoted by vl, vl,..., vr from head v1 to tail vr, then v1.distancev2.distance