Question: a) What does it mean for two simple graphs to be isomorphic?
b) What is meant by an invariant with respect to isomorphism for simple graphs? Give at least five examples of such invariants.
c) Give an example of two graphs that have the same numbers of vertices, edges, and degrees of vertices, but that are not isomorphic
d) Is a set of invariants known that can be used to effi- ciently determine whether two simple graphs are isomorphic?