Consider the following premises. If it is cold, then David is poor. David is not poor. Karen is taking a plane if and only if it is cold. Mary is a writer. If Mary were a writer, then Charles is rich. Can we infer the following from them? If we can, name the inference rule being used: Charles is not rich.
 From the fact that if it is cold, then David is poor, and that David is not poor we can infer that it is not cold via modus tollens. Finally, from the fact that if Mary were a writer, then Charles is rich, and that Mary is a writer we can infer that Charles is rich via modus ponens, which contradicts that Charles is not rich. Therefore, the answer is no.