Consider the following premises. For all x_11, if x_11 were a soldier, then x_11 is not taking a plane. For all x_11, x_11 will take a plane and x_11 is a cashier. For all x_11, x_11 is a soldier if and only if x_11 will play tennis. There is at least one x_11 for which x_11 will play tennis if and only if x_11 is an office clerk. Can we infer the following from them? If we can, name the inference rule being used: For all x_11, x_11 is an office clerk.
 From the fact that for all x_11, x_11 will take a plane and x_11 is a cashier we can infer that for all x_11, x_11 will take a plane via universal simplification. From the fact that for all x_11, if x_11 were a soldier, then x_11 is not taking a plane, and that for all x_11, x_11 will take a plane we can infer that for all x_11, x_11 is not a soldier via universal modus tollens. From the fact that for all x_11, x_11 is a soldier if and only if x_11 will play tennis, and that for all x_11, x_11 is not a soldier we can infer that for all x_11, x_11 will not play tennis via universal biconditional elimination. Finally, from the fact that there is at least one x_11 for which x_11 will play tennis if and only if x_11 is an office clerk, and that for all x_11, x_11 will not play tennis we can infer that there is at least one x_11 for which x_11 is not an office clerk via existential biconditional elimination, which contradicts that For all x_11, x_11 is an office clerk. Therefore, the answer is no.