Trigonal Planar | Structure & Examples

9.7 Give an example of each of the following or explain why no such example exists.(a) a planar graph of order 4.(b) a nonplanar graph of order 4.(c) a nonplanar graph of order 6 that contains neither K5 nor K3,3 as a subgraph.(d) a plane graph having 5 vertices, 10 edges and 7 regions.(e) a planar graph of order n ≥ 3 and size m with m = 3n - 6.(f) a nonplanar graph of order n ≥ 3 and size m with m = 3n - 6.

Show that every planar graph is a union of three forests.