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 y, y is a nurse if and only if y is a janitor. Sarah is a janitor or Sarah is not a nurse.
If Sarah were a nurse, then Sarah is a janitor can be inferred via the rewriting rule. For all y, if y were a nurse, then y is a janitor can be inferred via the universal biconditional elimination rule. For all y, if y were a janitor, then y is a nurse can be inferred via the universal biconditional elimination rule.