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 it rains, then John is taking a plane. John is taking a plane if and only if Richard is drinking water. If Richard drinks water, then it is raining. If John takes a plane, then Richard is drinking water.
If it rains, then Richard is drinking water can be inferred via the transitivity rule. If Richard drinks water, then John is taking a plane can be inferred via the transitivity rule. If John takes a plane, then it is raining can be inferred via the transitivity rule. If John takes a plane, then Richard is drinking water can be inferred via the biconditional elimination rule. If Richard drinks water, then John is taking a plane can be inferred via the biconditional elimination rule.