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 Charles were a mechanic, then it is snowing. It is snowing if and only if it is raining. If it rains, then Charles is a mechanic.
If it rains, then it is snowing can be inferred via the transitivity rule. If it snows, then it is raining can be inferred via the biconditional elimination rule. If it rains, then it is snowing can be inferred via the biconditional elimination rule.