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_11, x_11 will write a letter or x_11 will sleep. For all x_11, x_11 is not a soldier. There is at least one x_11 for which x_11 will not write a letter. For all x_11, x_11 is a soldier or x_11 is a sailor.
For all x_11, x_11 is a sailor can be inferred via the universal disjunctive syllogism rule. There is at least one x_11 for which x_11 will sleep can be inferred via the existential disjunctive syllogism rule.