Consider the following premises. There is at least one x_9 for which x_9 is a police officer if and only if x_9 will play a game. For all x_9, x_9 will play squash. For all x_9, x_9 will sleep. For all x_9, if x_9 plays a game, then x_9 is not sleeping. Can we infer the following from them? If we can, name the inference rule being used: For all x_9, x_9 is a police officer.
 From the fact that for all x_9, x_9 will sleep, and that for all x_9, x_9 will play squash we can infer that for all x_9, x_9 will sleep and x_9 will play squash via universal conjunction. From the fact that for all x_9, x_9 will sleep and x_9 will play squash we can infer that for all x_9, x_9 will sleep via universal simplification. From the fact that for all x_9, if x_9 plays a game, then x_9 is not sleeping, and that for all x_9, x_9 will sleep we can infer that for all x_9, x_9 will not play a game via universal modus tollens. Finally, from the fact that there is at least one x_9 for which x_9 is a police officer if and only if x_9 will play a game, and that for all x_9, x_9 will not play a game we can infer that there is at least one x_9 for which x_9 is not a police officer via existential biconditional elimination, which contradicts that For all x_9, x_9 is a police officer. Therefore, the answer is no.