Consider the following premises. If it is windy, then Richard is fast. If Richard were fast, then it is windy. If Richard were fast, then Robert is running. If Robert goes running, then it is windy. Can we infer the following from them? If we can, name the inference rule being used: It is windy if and only if Richard is fast.
 From the fact that if Richard were fast, then Robert is running, and that if Robert goes running, then it is windy we can infer that if Richard were fast, then it is windy via transitivity. Finally, from the fact that if it is windy, then Richard is fast, and that if Richard were fast, then it is windy we can infer that it is windy if and only if Richard is fast via biconditional introduction. Therefore, the answer is yes.