Consider the following premises. For all x_4, x_4 is fast if and only if x_4 is a bartender. For all x_4, if x_4 were fast, then x_4 is sad. Can we infer the following from them? For all x_4, if x_4 were a bartender, then x_4 is sad.
 From the fact that for all x_4, x_4 is fast if and only if x_4 is a bartender we can infer that for all x_4, if x_4 were a bartender, then x_4 is fast. Finally, from the fact that for all x_4, if x_4 were a bartender, then x_4 is fast, and that for all x_4, if x_4 were fast, then x_4 is sad we can infer that for all x_4, if x_4 were a bartender, then x_4 is sad. Therefore, the answer is yes.