Let G (V, E) denote an weighted undirected graph, in which every edge has unit weight, and let T = (V, E') denote the minimum spanning tree of G. Prove formally that a) for all u, v E V, the path between u and u in tree T is unique (10 Points) b) the graph G need not have a unique tree T (10 Points) Prove formally that Huffman code computation problem is in NP. (10 Points)