Consider the following premises. If Joseph were an office clerk, then Jennifer is working. For all y_2, if y_2 works, then y_2 is not a police officer. For all y_2, y_2 is a police officer. Can we infer the following from them? Joseph is not an office clerk.
 From the fact that for all y_2, if y_2 works, then y_2 is not a police officer, and that for all y_2, y_2 is a police officer we can infer that for all y_2, y_2 will not work. From the fact that for all y_2, y_2 will not work we can infer that Jennifer is not working. Finally, from the fact that if Joseph were an office clerk, then Jennifer is working, and that Jennifer is not working we can infer that Joseph is not an office clerk. Therefore, the answer is yes.