Consider the following premises. For all x_8, x_8 is curious. For all x_8, if x_8 were curious, then x_8 is listening to a song. For all x_8, x_8 will not listen to a song. Can we infer the following from them? There is at least one z for which z will play tennis.
 From the fact that for all x_8, if x_8 were curious, then x_8 is listening to a song, and that for all x_8, x_8 will not listen to a song we can infer that for all x_8, x_8 is not curious. From the fact that for all x_8, x_8 is curious we can infer that for all x_8, x_8 is curious or x_8 will play tennis. From the fact that for all x_8, x_8 is curious or x_8 will play tennis, and that for all x_8, x_8 is not curious we can infer that for all x_8, x_8 will play tennis. From the fact that for all x_8, x_8 will play tennis we can infer that David is playing tennis. Finally, from the fact that David is playing tennis we can infer that there is at least one z for which z will play tennis. Therefore, the answer is yes. Notice, however, that the premises were contradictory, so we can infer anything from them.