What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one z for which if z were a police officer, then z is a doctor. For all z, if z were a doctor, then z is a police officer.
There is at least one z for which z is a police officer if and only if z is a doctor. There is at least one z for which z is a doctor if and only if z is a police officer.