What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? It is overcast if and only if it is sunny. It is raining if and only if Barbara is listening to a song. It is not sunny. If it rains, then it is overcast.
If it is overcast, then it is sunny. If it rains, then Barbara is listening to a song. If it is sunny, then it is overcast. If Barbara listens to a song, then it is raining. It is not overcast.