Consider the following premises. Susan is reading a book. If it is cold, then Mary is not sleeping. For all x_18, x_18 will sleep. Can we infer the following from them? If we can, name the inference rule being used: It is cold.
 From the fact that for all x_18, x_18 will sleep we can infer that Mary is sleeping via universal instantiation. Finally, from the fact that if it is cold, then Mary is not sleeping, and that Mary is sleeping we can infer that it is not cold via modus tollens, which contradicts that It is cold. Therefore, the answer is no.