Consider the following premises. For all x_2, x_2 is a soldier if and only if x_2 is fast. Can we infer the following from them? If we can, name the inference rule being used: If Karen were a soldier, then Karen is fast.
 From the fact that for all x_2, x_2 is a soldier if and only if x_2 is fast we can infer that Karen is a soldier if and only if Karen is fast via universal instantiation. Finally, from the fact that Karen is a soldier if and only if Karen is fast we can infer that if Karen were a soldier, then Karen is fast via biconditional elimination. Therefore, the answer is yes.