What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one x_13 for which x_13 will take a plane. For all x_13, x_13 will play tennis if and only if x_13 will take a plane.
For all x_13, if x_13 plays tennis, then x_13 is taking a plane. For all x_13, if x_13 takes a plane, then x_13 is playing tennis.