4. Solve the following, including explaining your thought process/reasoning: Three professors are seated in a restaurant. The hostess comes to their table and asks them: "Does everyone want coffee?" The first professor answers: "I don't know." The second professor then adds: "I don't know." Finally, the third professor says: "No, not everyone wants coffee." The hostess comes back and gives coffee to the professors who want it. How did she figure out who wanted coffee?