Consider the following premises. For all y, if y were a police officer, then y is playing tennis. For all y, if y were a police officer, then y is working. There is at least one y for which y will not work. For all y, if y plays tennis, then y is a police officer. Can we infer the following from them? For all y, y will play tennis.
 From the fact that for all y, if y plays tennis, then y is a police officer, and that for all y, if y were a police officer, then y is playing tennis we can infer that for all y, y will play tennis if and only if y is a police officer. From the fact that for all y, y will play tennis if and only if y is a police officer we can infer that for all y, if y plays tennis, then y is a police officer. From the fact that for all y, if y plays tennis, then y is a police officer, and that for all y, if y were a police officer, then y is working we can infer that for all y, if y plays tennis, then y is working. Finally, from the fact that for all y, if y plays tennis, then y is working, and that there is at least one y for which y will not work we can infer that there is at least one y for which y will not play tennis, which contradicts that For all y, y will play tennis. Therefore, the answer is no.