Consider the following premises. For all x_9, if x_9 writes a letter, then x_9 is sleeping. There is at least one x_9 for which if x_9 sleeps, then x_9 is writing a letter. For all x_9, x_9 will sleep if and only if x_9 is a taxi driver. For all x_9, x_9 is not a taxi driver. Can we infer the following from them? For all x_9, x_9 will write a letter.
 From the fact that for all x_9, x_9 will sleep if and only if x_9 is a taxi driver we can infer that for all x_9, if x_9 sleeps, then x_9 is a taxi driver. From the fact that for all x_9, if x_9 writes a letter, then x_9 is sleeping, and that there is at least one x_9 for which if x_9 sleeps, then x_9 is writing a letter we can infer that there is at least one x_9 for which x_9 will write a letter if and only if x_9 will sleep. From the fact that for all x_9, if x_9 sleeps, then x_9 is a taxi driver, and that for all x_9, x_9 is not a taxi driver we can infer that for all x_9, x_9 will not sleep. Finally, from the fact that there is at least one x_9 for which x_9 will write a letter if and only if x_9 will sleep, and that for all x_9, x_9 will not sleep we can infer that there is at least one x_9 for which x_9 will not write a letter, which contradicts that For all x_9, x_9 will write a letter. Therefore, the answer is no.