Consider the following premises. There is at least one z_3 for which z_3 is a bartender if and only if z_3 is a sailor. For all z_3, z_3 is a police officer if and only if z_3 is a bartender. For all z_3, if z_3 were a sailor, then z_3 is a police officer. Can we infer the following from them? There is at least one z_3 for which if z_3 were a sailor, then z_3 is a bartender.
 From the fact that for all z_3, z_3 is a police officer if and only if z_3 is a bartender we can infer that for all z_3, if z_3 were a police officer, then z_3 is a bartender. From the fact that for all z_3, if z_3 were a sailor, then z_3 is a police officer, and that for all z_3, if z_3 were a police officer, then z_3 is a bartender we can infer that for all z_3, if z_3 were a sailor, then z_3 is a bartender. From the fact that there is at least one z_3 for which z_3 is a bartender if and only if z_3 is a sailor we can infer that there is at least one z_3 for which if z_3 were a bartender, then z_3 is a sailor. From the fact that for all z_3, if z_3 were a sailor, then z_3 is a bartender, and that there is at least one z_3 for which if z_3 were a bartender, then z_3 is a sailor we can infer that there is at least one z_3 for which z_3 is a sailor if and only if z_3 is a bartender. Finally, from the fact that there is at least one z_3 for which z_3 is a sailor if and only if z_3 is a bartender we can infer that there is at least one z_3 for which if z_3 were a sailor, then z_3 is a bartender. Therefore, the answer is yes.