What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z, z is a bartender if and only if z is a nurse. For all z, z is a bartender if and only if z is a nurse.
For all z, if z were a bartender, then z is a nurse. For all z, if z were a bartender, then z is a nurse. For all z, if z were a nurse, then z is a bartender. For all z, if z were a nurse, then z is a bartender.