Consider a graph with n nodes. Usually, when graphs are represented as adjacency matrices, algorithms require time little omega(n^2) (this means, at least n^2 time) because it takes that long to look at every location in the matrix. This problem explores an exception. Show that deciding whether a directed graph G contains a universal sink a vertex with in-degree n1 and out-degree 0 is possible in time O(n) when the graph is given as an adjacency matrix.