What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: There is at least one z_2 for which z_2 is a police officer if and only if z_2 will sleep. For all z_2, z_2 will not sleep. For all z_2, if z_2 were a police officer, then z_2 is reading a book. For all z_2, if z_2 reads a book, then z_2 is sleeping.
For all z_2, z_2 will not read a book can be inferred via the universal modus tollens rule. For all z_2, if z_2 were a police officer, then z_2 is sleeping can be inferred via the universal transitivity rule. There is at least one z_2 for which if z_2 were a police officer, then z_2 is sleeping can be inferred via the existential biconditional elimination rule. There is at least one z_2 for which if z_2 sleeps, then z_2 is a police officer can be inferred via the existential biconditional elimination rule. There is at least one z_2 for which z_2 is not a police officer can be inferred via the existential biconditional elimination rule.