Consider the following premises. For all x_9, x_9 will cook and x_9 will climb a mountain. For all x_9, if x_9 writes a letter, then x_9 is not taking a plane. For all x_9, if x_9 were a police officer, then x_9 is taking a plane. For all x_9, if x_9 cooks, then x_9 is taking a plane. Can we infer the following from them? For all x_9, x_9 will not write a letter.
 From the fact that for all x_9, x_9 will cook and x_9 will climb a mountain we can infer that for all x_9, x_9 will cook. From the fact that for all x_9, x_9 will cook we can infer that for all x_9, x_9 will cook or x_9 is a police officer. From the fact that for all x_9, if x_9 cooks, then x_9 is taking a plane, that for all x_9, if x_9 were a police officer, then x_9 is taking a plane, and that for all x_9, x_9 will cook or x_9 is a police officer we can infer that for all x_9, x_9 will take a plane. Finally, from the fact that for all x_9, if x_9 writes a letter, then x_9 is not taking a plane, and that for all x_9, x_9 will take a plane we can infer that for all x_9, x_9 will not write a letter. Therefore, the answer is yes.