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 not snowing. If it snows, then Barbara is rich. If Barbara were rich, then it is snowing. If Barbara were rich, then it is snowing.
Barbara is not rich can be inferred via the modus tollens rule. Barbara is not rich can be inferred via the modus tollens rule. It is snowing if and only if Barbara is rich can be inferred via the biconditional introduction rule. It is snowing if and only if Barbara is rich can be inferred via the biconditional introduction rule. Barbara is rich if and only if it is snowing can be inferred via the biconditional introduction rule. Barbara is rich if and only if it is snowing can be inferred via the biconditional introduction rule.