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, if z climbs a mountain, then z is a writer. For all z, z is rich. For all z, z is a server or z will climb a mountain. For all z, if z were a server, then z is a writer.
For all z, z is a writer can be inferred via the universal disjunction elimination rule.