What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z_4, z_4 is a sailor if and only if z_4 is a politician. For all z_4, if z_4 were a politician, then z_4 is a sailor.
For all z_4, if z_4 were a sailor, then z_4 is a politician. For all z_4, if z_4 were a politician, then z_4 is a sailor.