Consider the following premises. For all x_6, if x_6 makes tea, then x_6 is writing a letter. For all x_6, if x_6 writes a letter, then x_6 is an astronaut. For all x_6, if x_6 were an astronaut, then x_6 is a mechanic. For all x_6, if x_6 were a mechanic, then x_6 is making tea. Can we infer the following from them? There is at least one x_6 for which the fact that x_6 writes a letter does not imply that x_6 is making tea.
 From the fact that for all x_6, if x_6 were an astronaut, then x_6 is a mechanic, and that for all x_6, if x_6 were a mechanic, then x_6 is making tea we can infer that for all x_6, if x_6 were an astronaut, then x_6 is making tea. From the fact that for all x_6, if x_6 writes a letter, then x_6 is an astronaut, and that for all x_6, if x_6 were an astronaut, then x_6 is making tea we can infer that for all x_6, if x_6 writes a letter, then x_6 is making tea. From the fact that for all x_6, if x_6 writes a letter, then x_6 is making tea, and that for all x_6, if x_6 makes tea, then x_6 is writing a letter we can infer that for all x_6, x_6 will write a letter if and only if x_6 will make tea. Finally, from the fact that for all x_6, x_6 will write a letter if and only if x_6 will make tea we can infer that for all x_6, if x_6 writes a letter, then x_6 is making tea, which contradicts that There is at least one x_6 for which the fact that x_6 writes a letter does not imply that x_6 is making tea. Therefore, the answer is no.