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 x_9, x_9 is a janitor and x_9 is a server. For all x_5, if x_5 were a janitor, then x_5 is happy.
For all x_9, x_9 is a janitor can be inferred via the universal simplification rule. For all x_9, x_9 is a server can be inferred via the universal simplification rule.