Problem 2: The set {a,b,c,d,e,f,g} is a vertex cover, but it is not a minimum vertex cover. Remember that for a bipartite graph, the size of the min vertex cover is equal to the size of a max matching, which in this case is 6. Problem 3: (c) Remember to include y_i >= 0 for all i in your constraints. (d) Remember to check that the objective function value for the primal is equal to the objective function value for the dual. This can quickly tell you whether you made a mistake in calculating the optimum solutions.