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 plays a game, then x_9 is a janitor. For all x_9, x_9 is not a janitor. Richard is playing a game.
Since the premises are contradictory, we can infer anything from them.