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: For all z_2, z_2 is sad or z_2 will not read a book. For all z_2, z_2 will read a book if and only if z_2 is sad.
For all z_2, if z_2 reads a book, then z_2 is sad can be inferred via the universal rewriting rule. For all z_2, if z_2 reads a book, then z_2 is sad can be inferred via the universal biconditional elimination rule. For all z_2, if z_2 were sad, then z_2 is reading a book can be inferred via the universal biconditional elimination rule.