What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Joseph is a janitor if and only if John is listening to a song. Joseph is not a janitor. Karen is sleeping and it is windy.
Karen is sleeping. It is windy. If Joseph were a janitor, then John is listening to a song. If John listens to a song, then Joseph is a janitor. John is not listening to a song.