Consider the following premises. For all z_4, z_4 will take a plane if and only if z_4 is an office clerk. There is at least one z_4 for which z_4 will take a plane if and only if z_4 is excited. For all z_4, z_4 is not an office clerk. Can we infer the following from them? For all z_4, z_4 is excited.
 From the fact that for all z_4, z_4 will take a plane if and only if z_4 is an office clerk we can infer that for all z_4, if z_4 takes a plane, then z_4 is an office clerk. From the fact that for all z_4, if z_4 takes a plane, then z_4 is an office clerk, and that for all z_4, z_4 is not an office clerk we can infer that for all z_4, z_4 will not take a plane. Finally, from the fact that there is at least one z_4 for which z_4 will take a plane if and only if z_4 is excited, and that for all z_4, z_4 will not take a plane we can infer that there is at least one z_4 for which z_4 is not excited, which contradicts that For all z_4, z_4 is excited. Therefore, the answer is no.