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 sleeps, then z is a janitor. There is at least one z for which z will sleep if and only if z is a janitor.
There is at least one z for which if z sleeps, then z is a janitor can be inferred via the existential biconditional elimination rule. There is at least one z for which if z were a janitor, then z is sleeping can be inferred via the existential biconditional elimination rule.