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 police officer and x_9 will cook. For all x_9, x_9 is not sad. For all x_9, x_9 is sad or x_9 is a doctor.
For all x_9, x_9 is a doctor can be inferred via the universal disjunctive syllogism rule. For all x_9, x_9 is a police officer can be inferred via the universal simplification rule. For all x_9, x_9 will cook can be inferred via the universal simplification rule.