Consider the following premises. For all y, if y reads a book, then y is taking a plane. For all y, if y were an office clerk, then y is taking a plane. For all y, y is an office clerk or y will not take a plane. For all y, y will not read a book. For all y, if y takes a plane, then y is reading a book. Can we infer the following from them? If we can, name the inference rule being used: There is at least one y for which y is an office clerk.
 From the fact that for all y, if y reads a book, then y is taking a plane, and that for all y, if y takes a plane, then y is reading a book we can infer that for all y, y will read a book if and only if y will take a plane via universal biconditional introduction. From the fact that for all y, y is an office clerk or y will not take a plane we can infer that for all y, if y takes a plane, then y is an office clerk via universal rewriting. From the fact that for all y, if y were an office clerk, then y is taking a plane, and that for all y, if y takes a plane, then y is an office clerk we can infer that for all y, y is an office clerk if and only if y will take a plane via universal biconditional introduction. From the fact that for all y, y will read a book if and only if y will take a plane, and that for all y, y will not read a book we can infer that for all y, y will not take a plane via universal biconditional elimination. Finally, from the fact that for all y, y is an office clerk if and only if y will take a plane, and that for all y, y will not take a plane we can infer that for all y, y is not an office clerk via universal biconditional elimination, which contradicts that There is at least one y for which y is an office clerk. Therefore, the answer is no.