Consider the following premises. For all y, if y were a police officer, then y is an office clerk. For all y, if y climbs a mountain, then y is an office clerk. There is at least one y for which y is a police officer or y will climb a mountain. For all y, if y were an office clerk, then y is climbing a mountain. Can we infer the following from them? For all y, y is not an office clerk.
 From the fact that for all y, if y were an office clerk, then y is climbing a mountain, and that for all y, if y climbs a mountain, then y is an office clerk we can infer that for all y, y is an office clerk if and only if y will climb a mountain. From the fact that for all y, y is an office clerk if and only if y will climb a mountain we can infer that for all y, if y climbs a mountain, then y is an office clerk. Finally, from the fact that for all y, if y were a police officer, then y is an office clerk, that for all y, if y climbs a mountain, then y is an office clerk, and that there is at least one y for which y is a police officer or y will climb a mountain we can infer that there is at least one y for which y is an office clerk, which contradicts that For all y, y is not an office clerk. Therefore, the answer is no.