Consider the following premises. If it is cloudy, then Mary is a police officer. For all x_10, if x_10 were a police officer, then x_10 is an office clerk. Mary is not an office clerk. Can we infer the following from them? It is not cloudy.
 From the fact that for all x_10, if x_10 were a police officer, then x_10 is an office clerk we can infer that if Mary were a police officer, then Mary is an office clerk. From the fact that if it is cloudy, then Mary is a police officer, and that if Mary were a police officer, then Mary is an office clerk we can infer that if it is cloudy, then Mary is an office clerk. Finally, from the fact that if it is cloudy, then Mary is an office clerk, and that Mary is not an office clerk we can infer that it is not cloudy. Therefore, the answer is yes.