2. (15 pts] Let 91 = (V1, E1) and 92 = (V2, E2) be two graphs. We say that 91 and 92 are isomorphic if there exists a one-to-one and onto function f : V1 + V2 such that Vu, v, {u, v} E H {f(u), f(v)} E2.We call such a function f isomorphism. 1. Given an example of two graphs (their node names are different), both on four nodes, that are isomorphic. Explain why they are isomorphic. 2. Given an example of two graphs (their node names are different), both on four nodes, that are not isomorphic. Explain why they are not isomorphic. 3. Let 91, 92, 93 be three graphs such that 91 and 92 are isomorphic and 92 and 93 are isomorphic. Show that 91 and 93 are isomorphic by formally describing the isomorphism function and proving that it is indeed an isomorphism