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