5. (6 points) Consider the following two graphs $G$ and $H$:

(a) (2 points) Are graphs $G$ and $H$ isomorphic?

(b) (4 points) If they are isomorphic, please provide the isomorphism function (a mapping from the vertices of $G$ to the vertices of $H$ that preserves adjacency). If they are not, explain in detail why they are not isomorphic.