Consider the following premises. For all x_6, if x_6 writes a letter, then x_6 is not sleeping. There is at least one x_6 for which x_6 will sleep and x_6 will drink water. Can we infer the following from them? For all x_6, x_6 will write a letter.
 From the fact that there is at least one x_6 for which x_6 will sleep and x_6 will drink water we can infer that there is at least one x_6 for which x_6 will sleep. Finally, from the fact that for all x_6, if x_6 writes a letter, then x_6 is not sleeping, and that there is at least one x_6 for which x_6 will sleep we can infer that there is at least one x_6 for which x_6 will not write a letter, which contradicts that For all x_6, x_6 will write a letter. Therefore, the answer is no.