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 not a nurse. For all z, z is a nurse if and only if z will climb a mountain.
For all z, if z were a nurse, then z is climbing a mountain. For all z, if z climbs a mountain, then z is a nurse. For all z, z will not climb a mountain.