What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Joseph is a politician if and only if Susan is a nurse. Joseph is not a politician. If Susan were a bartender, then Susan is a nurse. If Susan were a nurse, then Susan is a bartender.
Susan is a bartender if and only if Susan is a nurse. Susan is a nurse if and only if Susan is a bartender. If Joseph were a politician, then Susan is a nurse. If Susan were a nurse, then Joseph is a politician. Susan is not a nurse.