What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Susan climbs a mountain, then Joseph is sleeping. Joseph is not sleeping. If Joseph listens to a song, then David is working. David is working if and only if Joseph is listening to a song. David is working if and only if Susan is climbing a mountain.
Susan is not climbing a mountain. If David works, then Joseph is listening to a song. If David works, then Susan is climbing a mountain. If Joseph listens to a song, then David is working. If Susan climbs a mountain, then David is working.