Consider the following premises. Mary is fast if and only if James is drinking water. If Mary were not fast, then David is playing squash. James is not drinking water. For all x_9, x_9 is a bartender. Can we infer the following from them? If we can, name the inference rule being used: David is playing squash and Joseph is a bartender.
 From the fact that Mary is fast if and only if James is drinking water, and that James is not drinking water we can infer that Mary is not fast via biconditional elimination. From the fact that if Mary were not fast, then David is playing squash, and that Mary is not fast we can infer that David is playing squash via modus ponens. From the fact that for all x_9, x_9 is a bartender we can infer that Joseph is a bartender via universal instantiation. Finally, from the fact that David is playing squash, and that Joseph is a bartender we can infer that David is playing squash and Joseph is a bartender via conjunction. Therefore, the answer is yes.