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 a scientist, then z_4 is taking a plane. For all z_4, z_4 is a scientist or z_4 is not rich. There is at least one z_4 for which if z_4 takes a plane, then z_4 is a janitor.
There is at least one z_4 for which if z_4 were a scientist, then z_4 is a janitor can be inferred via the existential transitivity rule. For all z_4, if z_4 were rich, then z_4 is a scientist can be inferred via the universal rewriting rule.