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, if z drives a car, then z is a janitor. For all z, if z were a janitor, then z is playing a game. For all z, if z were a janitor, then z is driving a car. For all z, z will not play a game.
For all z, z is not a janitor can be inferred via the universal modus tollens rule. For all z, if z drives a car, then z is playing a game can be inferred via the universal transitivity rule. For all z, z will drive a car if and only if z is a janitor can be inferred via the universal biconditional introduction rule. For all z, z is a janitor if and only if z will drive a car can be inferred via the universal biconditional introduction rule.