Consider the following premises. If Charles were a soldier, then it is cold. If it is cold, then Robert is making tea. If Robert makes tea, then it is cold. If Robert makes tea, then Charles is a soldier. Can we infer the following from them? If we can, name the inference rule being used: Charles is a soldier if and only if Robert is making tea.
 From the fact that if Robert makes tea, then it is cold, and that if it is cold, then Robert is making tea we can infer that Robert is making tea if and only if it is cold via biconditional introduction. From the fact that Robert is making tea if and only if it is cold we can infer that if it is cold, then Robert is making tea via biconditional elimination. From the fact that if Charles were a soldier, then it is cold, and that if it is cold, then Robert is making tea we can infer that if Charles were a soldier, then Robert is making tea via transitivity. Finally, from the fact that if Charles were a soldier, then Robert is making tea, and that if Robert makes tea, then Charles is a soldier we can infer that Charles is a soldier if and only if Robert is making tea via biconditional introduction. Therefore, the answer is yes.