What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If William were a sailor, then it is snowing. If it snows, then William is a sailor. If William were a sailor, then it is snowing.
William is a sailor if and only if it is snowing. It is snowing if and only if William is a sailor. It is snowing if and only if William is a sailor. William is a sailor if and only if it is snowing.