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 not happy. For all x_4, x_4 is happy or x_4 will climb a mountain. There is at least one x_4 for which x_4 will not climb a mountain or x_4 is a police officer.
For all x_4, x_4 will climb a mountain can be inferred via the universal disjunctive syllogism rule.