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: Richard is drinking water or Jessica is climbing a mountain. If Robert plays tennis, then Thomas is not a sailor. If Richard drinks water, then Thomas is a cashier. If Thomas were a cashier, then Thomas is a sailor. If Jessica climbs a mountain, then Thomas is a sailor.
If Richard drinks water, then Thomas is a sailor can be inferred via the transitivity rule.