What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one z_4 for which z_4 will read a book if and only if z_4 will take a plane. For all z_4, z_4 will take a plane if and only if z_4 will read a book.
For all z_4, if z_4 takes a plane, then z_4 is reading a book. There is at least one z_4 for which if z_4 reads a book, then z_4 is taking a plane. For all z_4, if z_4 reads a book, then z_4 is taking a plane. There is at least one z_4 for which if z_4 takes a plane, then z_4 is reading a book.