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 server, then z is a politician. For all z, if z were a politician, then z is a server.
There is at least one z for which z is a server if and only if z is a politician can be inferred via the existential biconditional introduction rule. There is at least one z for which z is a politician if and only if z is a server can be inferred via the existential biconditional introduction rule.