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 nurse, then David is a sailor. If David were a sailor, then Mary is taking a plane. Mary is not taking a plane.
David is not a sailor can be inferred via the modus tollens rule. If Charles were a nurse, then Mary is taking a plane can be inferred via the transitivity rule.