What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Robert is not taking a plane. If David plays tennis, then Michael is drinking water. Michael is drinking water if and only if Robert is taking a plane. If Michael drinks water, then David is playing tennis.
David is playing tennis if and only if Michael is drinking water. Michael is drinking water if and only if David is playing tennis. If Michael drinks water, then Robert is taking a plane. If Robert takes a plane, then Michael is drinking water. Michael is not drinking water.