Intellectual Joke

A young man is touring Harvard campus and decides to ask for directions on how to get to the library. He finds a girl reading a book under a tree and says "Excuse me, can you tell me where the library's at?" She cringes and says "You should never end a sentence with a preposition." The young man look confused for a second and replies, "I'm sorry - can you tell me where the library's at... b**ch?"