What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Robert plays a game, then Sarah is taking a plane. For all x_17, x_17 will drive a car or x_17 will play a game. Sarah is taking a plane if and only if Robert is driving a car.
If Sarah takes a plane, then Robert is driving a car. If Robert drives a car, then Sarah is taking a plane.