What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? David is taking a plane. For all x_9, x_9 will go running if and only if x_9 will take a plane.
There is at least one x for which x will take a plane. For all x_9, if x_9 goes running, then x_9 is taking a plane. For all x_9, if x_9 takes a plane, then x_9 is running.