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_9, if x_9 drives a car, then x_9 is an artist. For all x_9, if x_9 were an artist, then x_9 is taking a plane. For all x_9, x_9 will take a plane if and only if x_9 is a taxi driver. For all x_9, x_9 will drive a car.
For all x_9, x_9 is an artist can be inferred via the universal modus ponens rule. For all x_9, if x_9 drives a car, then x_9 is taking a plane can be inferred via the universal transitivity rule. For all x_9, if x_9 takes a plane, then x_9 is a taxi driver can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 were a taxi driver, then x_9 is taking a plane can be inferred via the universal biconditional elimination rule.