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 sailor. For all x_9, x_9 will write a letter or x_9 will make tea. For all x_9, if x_9 makes tea, then x_9 is a soldier. For all x_9, if x_9 writes a letter, then x_9 is a soldier.
For all x_9, x_9 is a soldier can be inferred via the universal disjunction elimination rule.