Consider the following premises. For all x_9, if x_9 were an astronaut, then x_9 is a server. There is at least one x_9 for which if x_9 were fast, then x_9 is an astronaut. For all x_9, x_9 is fast if and only if x_9 is a scientist. For all x_9, x_9 is not a server. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_9 for which x_9 is not a scientist.
 From the fact that for all x_9, if x_9 were an astronaut, then x_9 is a server, and that for all x_9, x_9 is not a server we can infer that for all x_9, x_9 is not an astronaut via universal modus tollens. From the fact that there is at least one x_9 for which if x_9 were fast, then x_9 is an astronaut, and that for all x_9, x_9 is not an astronaut we can infer that there is at least one x_9 for which x_9 is not fast via existential modus tollens. Finally, from the fact that for all x_9, x_9 is fast if and only if x_9 is a scientist, and that there is at least one x_9 for which x_9 is not fast we can infer that there is at least one x_9 for which x_9 is not a scientist via existential biconditional elimination. Therefore, the answer is yes.