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 y for which y is fast if and only if y will take a plane. For all y, y will take a plane.
There is at least one y for which if y were fast, then y is taking a plane. There is at least one y for which if y takes a plane, then y is fast.