Tony knew there was a solution to his math problem in one of four textbooks. He got some information from his classmates about it: Andy: "The solution is in either book 1 or 2"; Billy: "The solution is in either book 3 or 4"; Charlie: "The solution is in book 4"; Danny: "There is no solution in book 3". Emily helped Tony by saying that only one of his classmates was right, and the other three were mistaken. Which book has the solution in it?