Consider the following premises. For all x_5, x_5 is a scientist. For all x_5, x_5 is a mechanic or x_5 is not a scientist. For all x_5, if x_5 writes a letter, then x_5 is a mechanic. Can we infer the following from them? For all x_5, x_5 is a mechanic.
 From the fact that for all x_5, x_5 is a scientist we can infer that for all x_5, x_5 is a scientist or x_5 will write a letter. From the fact that for all x_5, x_5 is a mechanic or x_5 is not a scientist we can infer that for all x_5, if x_5 were a scientist, then x_5 is a mechanic. Finally, from the fact that for all x_5, if x_5 were a scientist, then x_5 is a mechanic, that for all x_5, if x_5 writes a letter, then x_5 is a mechanic, and that for all x_5, x_5 is a scientist or x_5 will write a letter we can infer that for all x_5, x_5 is a mechanic. Therefore, the answer is yes.