What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Richard listens to a song, then Mary is sleeping. If Patricia works, then Richard is listening to a song. If Mary sleeps, then it is overcast. If it is overcast, then Patricia is working.
If Richard listens to a song, then it is overcast. If Patricia works, then Mary is sleeping. If Mary sleeps, then Patricia is working. If it is overcast, then Richard is listening to a song.