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 will sleep. For all x_4, x_4 will not cook or x_4 is a janitor. There is at least one x_4 for which x_4 will not sleep or x_4 will climb a mountain.
Nothing can be inferred from these premises.