Consider the following premises. For all x_7, x_7 will drive a car if and only if x_7 is a soldier. For all x_7, x_7 will take a plane if and only if x_7 will read a book. For all x_7, if x_7 were a soldier, then x_7 is reading a book. For all x_7, x_7 will not take a plane. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_7 for which x_7 will drive a car.
 From the fact that for all x_7, x_7 will take a plane if and only if x_7 will read a book, and that for all x_7, x_7 will not take a plane we can infer that for all x_7, x_7 will not read a book via universal biconditional elimination. From the fact that for all x_7, if x_7 were a soldier, then x_7 is reading a book, and that for all x_7, x_7 will not read a book we can infer that for all x_7, x_7 is not a soldier via universal modus tollens. Finally, from the fact that for all x_7, x_7 will drive a car if and only if x_7 is a soldier, and that for all x_7, x_7 is not a soldier we can infer that for all x_7, x_7 will not drive a car via universal biconditional elimination, which contradicts that There is at least one x_7 for which x_7 will drive a car. Therefore, the answer is no.