Consider the following premises. Susan is not sleeping. If it is cold, then Susan is sleeping. If Susan sleeps, then it is cold. Can we infer the following from them? If we can, name the inference rule being used: It is cold.
 From the fact that if Susan sleeps, then it is cold, and that if it is cold, then Susan is sleeping we can infer that Susan is sleeping if and only if it is cold via biconditional introduction. Finally, from the fact that Susan is sleeping if and only if it is cold, and that Susan is not sleeping we can infer that it is not cold via biconditional elimination, which contradicts that It is cold. Therefore, the answer is no.