What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_9, x_9 is a janitor if and only if x_9 is a police officer. If Joseph were a janitor, then Joseph is a police officer.
For all x_9, if x_9 were a janitor, then x_9 is a police officer. For all x_9, if x_9 were a police officer, then x_9 is a janitor.