Consider the following premises. It is late or Barbara is not curious. If it snows, then Barbara is curious. If it is late, then it is snowing. Can we infer the following from them? If we can, name the inference rule being used: It is snowing if and only if it is late.
 From the fact that it is late or Barbara is not curious we can infer that if Barbara were curious, then it is late via rewriting. From the fact that if it snows, then Barbara is curious, and that if Barbara were curious, then it is late we can infer that if it snows, then it is late via transitivity. Finally, from the fact that if it snows, then it is late, and that if it is late, then it is snowing we can infer that it is snowing if and only if it is late via biconditional introduction. Therefore, the answer is yes.