Suppose that we can compute the transitive closure of a directed acyclic graph in f (|V|, |E|) time, where f is a monotonically increasing function of |V| and |E|. Show that the time to compute the transitive closure G^* = (V, E^*) of a general directed graph G = (V, E) is then f (|V|, |E|) + O(V + E^*).