What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If it is cloudy, then Barbara is taking a plane. If Barbara takes a plane, then it is snowing. It is not snowing. If it snows, then it is cloudy.
Barbara is not taking a plane. If it is cloudy, then it is snowing. If Barbara takes a plane, then it is cloudy. If it snows, then Barbara is taking a plane.