Recall that, we will look at an alternative proof for NP-completeness of VERTEX-COVER. VERTEX-COVER={{G, k)| G = (V, E) is an undirected graph that has a vertex cover of size k}. A vertex cover is a subset S of V such for each each edge e= (u, v) EE at least one of u, v is in S. a) (3 points) Prove that VERTEX-COVER E NP. b) (7 points) Prove that INDEPENDENT-SET