Consider the following premises. For all x_10, x_10 is not a soldier. Charles is a scientist if and only if Sarah is running. Charles is a scientist if and only if Thomas is a soldier. Can we infer the following from them? If we can, name the inference rule being used: Sarah is running.
 From the fact that for all x_10, x_10 is not a soldier we can infer that Thomas is not a soldier via universal instantiation. From the fact that Charles is a scientist if and only if Thomas is a soldier, and that Thomas is not a soldier we can infer that Charles is not a scientist via biconditional elimination. Finally, from the fact that Charles is a scientist if and only if Sarah is running, and that Charles is not a scientist we can infer that Sarah is not running via biconditional elimination, which contradicts that Sarah is running. Therefore, the answer is no.