Consider the following premises. It is late if and only if David is drinking water. For all x, x will not drink water. Can we infer the following from them? It is not late.
 From the fact that for all x, x will not drink water we can infer that David is not drinking water. From the fact that it is late if and only if David is drinking water we can infer that if it is late, then David is drinking water. Finally, from the fact that if it is late, then David is drinking water, and that David is not drinking water we can infer that it is not late. Therefore, the answer is yes.