Consider the following premises. Jennifer is writing a letter if and only if Susan is a taxi driver. Jennifer is not writing a letter. If Charles were a nurse, then Susan is a taxi driver. If Charles were not a nurse, then it is overcast. Can we infer the following from them? If we can, name the inference rule being used: It is not overcast.
 From the fact that Jennifer is writing a letter if and only if Susan is a taxi driver, and that Jennifer is not writing a letter we can infer that Susan is not a taxi driver via biconditional elimination. From the fact that if Charles were a nurse, then Susan is a taxi driver, and that Susan is not a taxi driver we can infer that Charles is not a nurse via modus tollens. Finally, from the fact that if Charles were not a nurse, then it is overcast, and that Charles is not a nurse we can infer that it is overcast via modus ponens, which contradicts that It is not overcast. Therefore, the answer is no.