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 will write a letter or z_2 is not a janitor. There is at least one z_2 for which if z_2 writes a letter, then z_2 is a janitor.
For all z_2, if z_2 were a janitor, then z_2 is writing a letter can be inferred via the universal rewriting rule.