What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: There is at least one z for which if z were a nurse, then z is a sailor. For all z, z is a nurse if and only if z is a sailor.
For all z, if z were a nurse, then z is a sailor can be inferred via the universal biconditional elimination rule. For all z, if z were a sailor, then z is a nurse can be inferred via the universal biconditional elimination rule.