What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Robert is excited if and only if Barbara is taking a plane. If it is sunny, then Elisabeth is not driving a car. It is sunny if and only if Robert is excited. Elisabeth is driving a car.
It is not sunny. If Robert were excited, then Barbara is taking a plane. If it is sunny, then Robert is excited. If Barbara takes a plane, then Robert is excited. If Robert were excited, then it is sunny.