What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? It is not sunny. If it is sunny, then it is cold. If it is cold, then it is overcast. If it is overcast, then it is sunny. It is cold if and only if William is a janitor.
It is not overcast. If it is sunny, then it is overcast. If it is cold, then it is sunny. If it is overcast, then it is cold. If it is cold, then William is a janitor. If William were a janitor, then it is cold.