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: If it is late, then Patricia is a janitor. If Patricia were a janitor, then it is late. If Barbara were a doctor, then Patricia is a janitor. It is not late.
Patricia is not a janitor can be inferred via the modus tollens rule. If Barbara were a doctor, then it is late can be inferred via the transitivity rule. It is late if and only if Patricia is a janitor can be inferred via the biconditional introduction rule. Patricia is a janitor if and only if it is late can be inferred via the biconditional introduction rule.