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: It is late or Charles is a janitor. It is raining if and only if it is late. If it rains, then it is late. If Charles were a janitor, then it is raining.
If Charles were a janitor, then it is late can be inferred via the transitivity rule. If it rains, then it is late can be inferred via the biconditional elimination rule. If it is late, then it is raining can be inferred via the biconditional elimination rule.