What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If William reads a book, then Barbara is playing a game. It is sunny if and only if it is snowing. If it snows, then William is reading a book. Barbara is not playing a game.
William is not reading a book. If it is sunny, then it is snowing. If it snows, then it is sunny.