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