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: Robert is not driving a car. If Barbara were a nurse, then David is taking a plane. If David takes a plane, then Robert is driving a car.
David is not taking a plane can be inferred via the modus tollens rule. If Barbara were a nurse, then Robert is driving a car can be inferred via the transitivity rule.