Consider the following premises. For all x_4, if x_4 were a police officer, then x_4 is playing squash. There is at least one x_4 for which x_4 will take a plane or x_4 is a police officer. For all x_4, x_4 will not take a plane or x_4 is a mechanic. For all x_4, x_4 will not play squash. Can we infer the following from them? There is at least one x_4 for which x_4 is a mechanic.
 From the fact that for all x_4, if x_4 were a police officer, then x_4 is playing squash, and that for all x_4, x_4 will not play squash we can infer that for all x_4, x_4 is not a police officer. From the fact that there is at least one x_4 for which x_4 will take a plane or x_4 is a police officer, and that for all x_4, x_4 will not take a plane or x_4 is a mechanic we can infer that there is at least one x_4 for which x_4 is a police officer or x_4 is a mechanic. Finally, from the fact that there is at least one x_4 for which x_4 is a police officer or x_4 is a mechanic, and that for all x_4, x_4 is not a police officer we can infer that there is at least one x_4 for which x_4 is a mechanic. Therefore, the answer is yes.