Consider the following premises. For all y, y will write a letter if and only if y will drink water. Linda is a bartender or David is not writing a letter. Linda is not a bartender. Can we infer the following from them? If we can, name the inference rule being used: David is drinking water.
 From the fact that for all y, y will write a letter if and only if y will drink water we can infer that David is writing a letter if and only if David is drinking water via universal instantiation. From the fact that Linda is a bartender or David is not writing a letter we can infer that if David writes a letter, then Linda is a bartender via rewriting. From the fact that if David writes a letter, then Linda is a bartender, and that Linda is not a bartender we can infer that David is not writing a letter via modus tollens. Finally, from the fact that David is writing a letter if and only if David is drinking water, and that David is not writing a letter we can infer that David is not drinking water via biconditional elimination, which contradicts that David is drinking water. Therefore, the answer is no.