What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_13, if x_13 goes running, then x_13 is fast. For all x_13, if x_13 takes a plane, then x_13 is fast. Sarah is working. For all x_13, x_13 will go running or x_13 will take a plane.
For all x_13, x_13 is fast.