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 x_4, if x_4 were an electrician, then x_4 is a politician. For all x_4, x_4 will not take a plane. For all x_4, if x_4 takes a plane, then x_4 is an electrician. For all x_4, if x_4 were a politician, then x_4 is taking a plane.
For all x_4, x_4 is not a politician can be inferred via the universal modus tollens rule. For all x_4, if x_4 were an electrician, then x_4 is taking a plane can be inferred via the universal transitivity rule. For all x_4, if x_4 takes a plane, then x_4 is a politician can be inferred via the universal transitivity rule. For all x_4, if x_4 were a politician, then x_4 is an electrician can be inferred via the universal transitivity rule.