Consider the following premises. For all z_3, z_3 is an office clerk if and only if z_3 will drive a car. For all z_3, z_3 will not drive a car. For all z_3, z_3 is an office clerk if and only if z_3 is fast. Can we infer the following from them? For all z_3, z_3 is not fast.
 From the fact that for all z_3, z_3 is an office clerk if and only if z_3 is fast we can infer that for all z_3, if z_3 were fast, then z_3 is an office clerk. From the fact that for all z_3, z_3 is an office clerk if and only if z_3 will drive a car, and that for all z_3, z_3 will not drive a car we can infer that for all z_3, z_3 is not an office clerk. Finally, from the fact that for all z_3, if z_3 were fast, then z_3 is an office clerk, and that for all z_3, z_3 is not an office clerk we can infer that for all z_3, z_3 is not fast. Therefore, the answer is yes.