What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: For all z_4, if z_4 were poor, then z_4 is curious. For all z_4, if z_4 were a cashier, then z_4 is poor. There is at least one z_4 for which z_4 is a cashier if and only if z_4 will take a plane. For all z_4, if z_4 were curious, then z_4 is taking a plane.
For all z_4, if z_4 were poor, then z_4 is taking a plane can be inferred via the universal transitivity rule. For all z_4, if z_4 were a cashier, then z_4 is curious can be inferred via the universal transitivity rule. There is at least one z_4 for which if z_4 were a cashier, then z_4 is taking a plane can be inferred via the existential biconditional elimination rule. There is at least one z_4 for which if z_4 takes a plane, then z_4 is a cashier can be inferred via the existential biconditional elimination rule.