This question is from " Networks, Crowds, and Markets: Reasoning about a Highly Connected World" textbook in chapter 2

(a) Give an example of a graph in which every node is pivotal for at least two dierent pairs of nodes. Explain your answer. (c) Give an example of a graph having at least four nodes in which there is a single node X that is pivotal for every pair of nodes (not counting pairs that include X). Explain your answer.