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: For all z, if z were an office clerk, then z is a sailor. There is at least one z for which if z were an office clerk, then z is a sailor. For all z, if z were a sailor, then z is an office clerk.
For all z, z is an office clerk if and only if z is a sailor can be inferred via the universal biconditional introduction rule. For all z, z is a sailor if and only if z is an office clerk can be inferred via the universal biconditional introduction rule. There is at least one z for which z is an office clerk if and only if z is a sailor can be inferred via the existential biconditional introduction rule. There is at least one z for which z is a sailor if and only if z is an office clerk can be inferred via the existential biconditional introduction rule.