An explorer is captured by a group of cannibals. There are two types of cannibals$-$those who always tell the truth and those who always lie. The cannibals will barbecue the explorer unless he can determine whether a particular cannibal always lies or always tells the truth. He is allowed to ask the cannibal exactly one question.

a$)$ Explain why the question "Are you a liar?" does not work.

b$)$ Find a question that the explorer can use to determine whether the cannibal always lies or always