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 x for which x is an astronaut if and only if x is a janitor. For all x, if x were a janitor, then x is an astronaut.
There is at least one x for which if x were an astronaut, then x is a janitor can be inferred via the existential biconditional elimination rule. There is at least one x for which if x were a janitor, then x is an astronaut can be inferred via the existential biconditional elimination rule.