Consider the following premises. For all x_5, x_5 will not play squash. For all x_5, x_5 is a police officer if and only if x_5 is fast. For all x_5, if x_5 were a police officer, then x_5 is playing squash. For all x_5, x_5 is a janitor if and only if x_5 is fast. Can we infer the following from them? For all x_5, x_5 is not a janitor.
 From the fact that for all x_5, if x_5 were a police officer, then x_5 is playing squash, and that for all x_5, x_5 will not play squash we can infer that for all x_5, x_5 is not a police officer. From the fact that for all x_5, x_5 is a police officer if and only if x_5 is fast, and that for all x_5, x_5 is not a police officer we can infer that for all x_5, x_5 is not fast. Finally, from the fact that for all x_5, x_5 is a janitor if and only if x_5 is fast, and that for all x_5, x_5 is not fast we can infer that for all x_5, x_5 is not a janitor. Therefore, the answer is yes.