Consider the following premises. Richard is a bartender if and only if Thomas is listening to a song. Richard is a bartender if and only if Thomas is listening to a song. Can we infer the following from them? If we can, name the inference rule being used: Thomas is listening to a song if and only if Richard is a bartender.
 From the fact that Richard is a bartender if and only if Thomas is listening to a song we can infer that if Thomas listens to a song, then Richard is a bartender via biconditional elimination. From the fact that Richard is a bartender if and only if Thomas is listening to a song we can infer that if Richard were a bartender, then Thomas is listening to a song via biconditional elimination. Finally, from the fact that if Thomas listens to a song, then Richard is a bartender, and that if Richard were a bartender, then Thomas is listening to a song we can infer that Thomas is listening to a song if and only if Richard is a bartender via biconditional introduction. Therefore, the answer is yes.