Consider the following premises. For all x_10, x_10 will drink water or x_10 will play tennis. If Robert drinks water, then David is a cashier. David is not a cashier. If David were a cashier, then Robert is drinking water. Can we infer the following from them? Robert is not playing tennis.
 From the fact that for all x_10, x_10 will drink water or x_10 will play tennis we can infer that Robert is drinking water or Robert is playing tennis. From the fact that if David were a cashier, then Robert is drinking water, and that if Robert drinks water, then David is a cashier we can infer that David is a cashier if and only if Robert is drinking water. From the fact that David is a cashier if and only if Robert is drinking water, and that David is not a cashier we can infer that Robert is not drinking water. Finally, from the fact that Robert is drinking water or Robert is playing tennis, and that Robert is not drinking water we can infer that Robert is playing tennis, which contradicts that Robert is not playing tennis. Therefore, the answer is no.