Consider the following premises. For all z, z will work if and only if z is an electrician. For all z, if z were an electrician, then z is playing squash. For all z, z will not work. For all z, if z plays squash, then z is an electrician. Can we infer the following from them? If we can, name the inference rule being used: There is at least one z for which z will play squash.
 From the fact that for all z, z will work if and only if z is an electrician we can infer that for all z, if z were an electrician, then z is working via universal biconditional elimination. From the fact that for all z, if z were an electrician, then z is working, and that for all z, z will not work we can infer that for all z, z is not an electrician via universal modus tollens. From the fact that for all z, if z were an electrician, then z is playing squash, and that for all z, if z plays squash, then z is an electrician we can infer that for all z, z is an electrician if and only if z will play squash via universal biconditional introduction. Finally, from the fact that for all z, z is an electrician if and only if z will play squash, and that for all z, z is not an electrician we can infer that for all z, z will not play squash via universal biconditional elimination, which contradicts that There is at least one z for which z will play squash. Therefore, the answer is no.