Consider the following premises. For all z_4, if z_4 were a bartender, then z_4 is an electrician. For all z_4, if z_4 were an electrician, then z_4 is a bartender. For all z_4, z_4 is not a bartender. Can we infer the following from them? For all z_4, z_4 is not an electrician.
 From the fact that for all z_4, if z_4 were an electrician, then z_4 is a bartender, and that for all z_4, if z_4 were a bartender, then z_4 is an electrician we can infer that for all z_4, z_4 is an electrician if and only if z_4 is a bartender. Finally, from the fact that for all z_4, z_4 is an electrician if and only if z_4 is a bartender, and that for all z_4, z_4 is not a bartender we can infer that for all z_4, z_4 is not an electrician. Therefore, the answer is yes.