Consider the following premises. For all z, if z works, then z is taking a plane. For all z, if z takes a plane, then z is a writer. For all z, z will work if and only if z will play squash. Can we infer the following from them? There is at least one z for which the fact that z plays squash does not imply that z is a writer.
 From the fact that for all z, if z works, then z is taking a plane, and that for all z, if z takes a plane, then z is a writer we can infer that for all z, if z works, then z is a writer. From the fact that for all z, z will work if and only if z will play squash we can infer that for all z, if z plays squash, then z is working. Finally, from the fact that for all z, if z plays squash, then z is working, and that for all z, if z works, then z is a writer we can infer that for all z, if z plays squash, then z is a writer, which contradicts that There is at least one z for which the fact that z plays squash does not imply that z is a writer. Therefore, the answer is no.