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 overcast, then Barbara is a lawyer. If Barbara were a lawyer, then it is cloudy. It is not cloudy. If Barbara were a lawyer, then it is overcast.
Barbara is not a lawyer can be inferred via the modus tollens rule. If it is overcast, then it is cloudy can be inferred via the transitivity rule. It is overcast if and only if Barbara is a lawyer can be inferred via the biconditional introduction rule. Barbara is a lawyer if and only if it is overcast can be inferred via the biconditional introduction rule.