Consider the following premises. If Charles were a politician, then Charles is drinking water. Jessica is a carpenter if and only if Richard is a nurse. If Charles drinks water, then Jessica is a carpenter. Can we infer the following from them? If we can, name the inference rule being used: The fact that Charles were a politician does not imply that Richard is a nurse.
 From the fact that Jessica is a carpenter if and only if Richard is a nurse we can infer that if Jessica were a carpenter, then Richard is a nurse via biconditional elimination. From the fact that if Charles drinks water, then Jessica is a carpenter, and that if Jessica were a carpenter, then Richard is a nurse we can infer that if Charles drinks water, then Richard is a nurse via transitivity. Finally, from the fact that if Charles were a politician, then Charles is drinking water, and that if Charles drinks water, then Richard is a nurse we can infer that if Charles were a politician, then Richard is a nurse via transitivity, which contradicts that The fact that Charles were a politician does not imply that Richard is a nurse. Therefore, the answer is no.