A tourist is enjoying an afternoon refreshment in a local eatery when the manager says to him Do you see those three men over there? One is Mr. X who always tells the truth. Another is Mr. Y who always lies. The third is Mr. Z who sometimes tells the truth and sometimes lies. You may ask them three Yes/No questions always indicating which man should answer. After asking these three questions, if you correctly identify Mr. X, Mr. Y and Mr. Z then your bill is on them. What Yes/No questions should the tourist ask?