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 z for which if z plays tennis, then z is a cashier. For all z, if z plays tennis, then z is taking a plane. For all z, if z takes a plane, then z is playing tennis.
There is at least one z for which if z takes a plane, then z is a cashier. For all z, z will play tennis if and only if z will take a plane. For all z, z will take a plane if and only if z will play tennis.