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 Elisabeth doesn't drink water, then David is taking a plane. If Michael plays squash, then Richard is a bartender. Richard is not a bartender. If Elisabeth drinks water, then Michael is playing squash.
Michael is not playing squash can be inferred via the modus tollens rule. If Elisabeth drinks water, then Richard is a bartender can be inferred via the transitivity rule.