What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y, y is a carpenter if and only if y is a janitor. There is at least one y for which if y were a carpenter, then y is a janitor. For all y, y is not a janitor.
There is at least one y for which y is not a carpenter. For all y, if y were a carpenter, then y is a janitor. For all y, if y were a janitor, then y is a carpenter. For all y, y is not a carpenter.