Consider the following premises. There is at least one x_9 for which x_9 will not take a plane. For all x_9, if x_9 were an artist, then x_9 is taking a plane. For all x_9, if x_9 sleeps, then x_9 is an artist. For all x_9, if x_9 takes a plane, then x_9 is an artist. Can we infer the following from them? If we can, name the inference rule being used: For all x_9, x_9 will sleep.
 From the fact that for all x_9, if x_9 were an artist, then x_9 is taking a plane, and that for all x_9, if x_9 takes a plane, then x_9 is an artist we can infer that for all x_9, x_9 is an artist if and only if x_9 will take a plane via universal biconditional introduction. From the fact that for all x_9, x_9 is an artist if and only if x_9 will take a plane, and that there is at least one x_9 for which x_9 will not take a plane we can infer that there is at least one x_9 for which x_9 is not an artist via existential biconditional elimination. Finally, from the fact that for all x_9, if x_9 sleeps, then x_9 is an artist, and that there is at least one x_9 for which x_9 is not an artist we can infer that there is at least one x_9 for which x_9 will not sleep via existential modus tollens, which contradicts that For all x_9, x_9 will sleep. Therefore, the answer is no.