(a) Given a flow network G = (V, E, s, t) with positive integer capacities Cuv, let d = min(u,v) EE Cuv. Either prove or disprove that the value of the maximum flow is an integer multiple of d. (b) Given a flow network G=(V, E, s, t) with positive integer capacities Cuv, let d = GCD({Cuv | (u, v) E E}). Either prove or disprove that the value of the maximum flow is an integer multiple of d. (c) Vertex cover SC V of a graph G = (V, E) is defined as the set of vertices such that every edge in the graph is incident to at least one of the vertices from the set S. The minimum vertex cover problem is to find an S with the maximum size. Give an integer linear program for the vertex cover problem.