Consider the following premises. For all y, if y drinks water, then y is taking a plane. There is at least one y for which y will drink water. For all y, y will drink water or y will not take a plane. Can we infer the following from them? There is at least one y for which y will take a plane.
 From the fact that for all y, y will drink water or y will not take a plane we can infer that for all y, if y takes a plane, then y is drinking water. From the fact that for all y, if y drinks water, then y is taking a plane, and that for all y, if y takes a plane, then y is drinking water we can infer that for all y, y will drink water if and only if y will take a plane. From the fact that for all y, y will drink water if and only if y will take a plane we can infer that for all y, if y drinks water, then y is taking a plane. Finally, from the fact that for all y, if y drinks water, then y is taking a plane, and that there is at least one y for which y will drink water we can infer that there is at least one y for which y will take a plane. Therefore, the answer is yes.