Consider the following undirected graph with edge weights as shown:

The number of minimum-weight spanning trees of the graph is ______

Breadth First Search $$(BFS)$$ is started on a binary tree beginning from the root vertex. There is a vertex $$t$$ at a distance four from the root. If t is the $$n$$-th vertex in this $$BFS$$ traversal, then the maximum possible value of $$n$$ is ___________.

Consider the following directed graph:

The number of different topological orderings of the vertices of the graph is ________________.

Let G be a graph with n vertices and m edges. What is the tightest upper bound on the running time of Depth First Search on G, when G is represented as an adjacency matrix?