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