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 Patricia were a janitor, then Sarah is climbing a mountain. Michael is not a lawyer or it is snowing. If it snows, then James is drinking water. Michael is a lawyer or David is running. Sarah is not climbing a mountain. If David goes running, then James is drinking water. If Patricia were not a janitor, then Barbara is writing a letter.
Patricia is not a janitor can be inferred via the modus tollens rule. David is running or it is snowing can be inferred via the resolution rule.