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, z is a bartender or z is not a scientist. There is at least one z for which z is a scientist if and only if z is a bartender.
For all z, if z were a scientist, then z is a bartender can be inferred via the universal rewriting rule. There is at least one z for which if z were a scientist, then z is a bartender can be inferred via the existential biconditional elimination rule. There is at least one z for which if z were a bartender, then z is a scientist can be inferred via the existential biconditional elimination rule.