Consider the following premises. Jennifer is excited or it is not late. If Jennifer were excited, then it is late. Jennifer is excited if and only if it is late. Can we infer the following from them? If we can, name the inference rule being used: If is not true that it is late if and only if Jennifer is excited.
 From the fact that Jennifer is excited or it is not late we can infer that if it is late, then Jennifer is excited via rewriting. Finally, from the fact that if it is late, then Jennifer is excited, and that if Jennifer were excited, then it is late we can infer that it is late if and only if Jennifer is excited via biconditional introduction, which contradicts that If is not true that it is late if and only if Jennifer is excited. Therefore, the answer is no.