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_4, x_4 is a nurse or x_4 will climb a mountain. For all x_4, if x_4 were a nurse, then x_4 is rich. For all x_4, if x_4 climbs a mountain, then x_4 is rich. For all x_4, x_4 will play tennis.
For all x_4, x_4 is rich can be inferred via the universal disjunction elimination rule.