What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? John is not a police officer. It is raining if and only if Charles is a doctor. If Charles were a doctor, then John is a police officer. If John were a police officer, then Charles is a doctor.
Charles is not a doctor. Charles is a doctor if and only if John is a police officer. John is a police officer if and only if Charles is a doctor. If it rains, then Charles is a doctor. If Charles were a doctor, then it is raining.