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: There is at least one x_3 for which if x_3 were a police officer, then x_3 is taking a plane. For all x_3, x_3 is not a police officer. For all x_3, if x_3 takes a plane, then x_3 is a scientist. For all x_3, if x_3 were a scientist, then x_3 is a police officer.
For all x_3, x_3 is not a scientist can be inferred via the universal modus tollens rule. For all x_3, if x_3 takes a plane, then x_3 is a police officer can be inferred via the universal transitivity rule. There is at least one x_3 for which if x_3 were a police officer, then x_3 is a scientist can be inferred via the existential transitivity rule. There is at least one x_3 for which if x_3 were a scientist, then x_3 is taking a plane can be inferred via the existential transitivity rule.