Problem 4. For each of the following conditions, either draw a simple graph with the required conditions,or show that no such graph can exist.(a) 6 vertices, 4 edges.(b) 5 vertices with degrees 1, 2, 2, 3, 4.(c) 6 vertices with degrees 1, 1, 2, 3, 4, 4.(d) 6 vertices with degrees 1, 1, 3, 4, 4, 5.