Consider the following premises. Susan is not a server. For all x_2, x_2 is a scientist if and only if x_2 is a server. Can we infer the following from them? If we can, name the inference rule being used: Susan is a scientist.
 From the fact that for all x_2, x_2 is a scientist if and only if x_2 is a server we can infer that Susan is a scientist if and only if Susan is a server via universal instantiation. From the fact that Susan is a scientist if and only if Susan is a server we can infer that if Susan were a scientist, then Susan is a server via biconditional elimination. Finally, from the fact that if Susan were a scientist, then Susan is a server, and that Susan is not a server we can infer that Susan is not a scientist via modus tollens, which contradicts that Susan is a scientist. Therefore, the answer is no.