Consider the following premises. It is cloudy. If Sarah takes a plane, then it is not cloudy. For all x_10, if x_10 writes a letter, then x_10 is taking a plane. Can we infer the following from them? Sarah is writing a letter.
 From the fact that for all x_10, if x_10 writes a letter, then x_10 is taking a plane we can infer that if Sarah writes a letter, then Sarah is taking a plane. From the fact that if Sarah takes a plane, then it is not cloudy, and that it is cloudy we can infer that Sarah is not taking a plane. Finally, from the fact that if Sarah writes a letter, then Sarah is taking a plane, and that Sarah is not taking a plane we can infer that Sarah is not writing a letter, which contradicts that Sarah is writing a letter. Therefore, the answer is no.