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: Richard is a cashier if and only if Charles is a musician. If Charles were a musician, then Richard is a cashier. It is snowing. If Charles were a musician, then it is not snowing.
Charles is not a musician can be inferred via the modus tollens rule. If Richard were a cashier, then Charles is a musician can be inferred via the biconditional elimination rule. If Charles were a musician, then Richard is a cashier can be inferred via the biconditional elimination rule.