Consider the following premises. John is playing a game. If John reads a book, then John is not playing a game. It is snowing if and only if John is reading a book. Can we infer the following from them? If we can, name the inference rule being used: It is snowing.
 From the fact that if John reads a book, then John is not playing a game, and that John is playing a game we can infer that John is not reading a book via modus tollens. Finally, from the fact that it is snowing if and only if John is reading a book, and that John is not reading a book we can infer that it is not snowing via biconditional elimination, which contradicts that It is snowing. Therefore, the answer is no.