Prof. Snape claims that when an adjacency matrix representation is used, most graph algorithms take ohm (V^2) time, but there are some exceptions. One such exception, Snape claims, is determining whether a directed graph G contains a black hole, which is defined as a vertex with in-degree |V| - 1 (i.e., every other vertex points to this one) and out-degree 0. Snape sourly claims that this determination can be made in time O(V), given an adjacency matrix for G. Prove that Snape is correct