What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_6, if x_6 takes a plane, then x_6 is excited. For all x_6, if x_6 were excited, then x_6 is taking a plane. For all x_6, if x_6 were excited, then x_6 is taking a plane.
For all x_6, x_6 will take a plane if and only if x_6 is excited. For all x_6, x_6 will take a plane if and only if x_6 is excited. For all x_6, x_6 is excited if and only if x_6 will take a plane. For all x_6, x_6 is excited if and only if x_6 will take a plane.