Consider the following premises. Barbara is poor or Thomas is not running. Thomas is running or Barbara is not poor. Can we infer the following from them? If we can, name the inference rule being used: Thomas is running if and only if Barbara is poor.
 From the fact that Barbara is poor or Thomas is not running we can infer that if Thomas goes running, then Barbara is poor via rewriting. From the fact that Thomas is running or Barbara is not poor we can infer that if Barbara were poor, then Thomas is running via rewriting. Finally, from the fact that if Thomas goes running, then Barbara is poor, and that if Barbara were poor, then Thomas is running we can infer that Thomas is running if and only if Barbara is poor via biconditional introduction. Therefore, the answer is yes.