Consider the following premises. There is at least one x_9 for which if x_9 sleeps, then x_9 is playing tennis. For all x_9, x_9 will sleep if and only if x_9 is curious. For all x_9, if x_9 plays tennis, then x_9 is reading a book. For all x_9, x_9 will not read a book. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_9 for which x_9 is not curious.
 From the fact that for all x_9, if x_9 plays tennis, then x_9 is reading a book, and that for all x_9, x_9 will not read a book we can infer that for all x_9, x_9 will not play tennis via universal modus tollens. From the fact that there is at least one x_9 for which if x_9 sleeps, then x_9 is playing tennis, and that for all x_9, x_9 will not play tennis we can infer that there is at least one x_9 for which x_9 will not sleep via existential modus tollens. Finally, from the fact that for all x_9, x_9 will sleep if and only if x_9 is curious, and that there is at least one x_9 for which x_9 will not sleep we can infer that there is at least one x_9 for which x_9 is not curious via existential biconditional elimination. Therefore, the answer is yes.