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_13, if x_13 drinks water, then x_13 is not taking a plane. For all x_13, x_13 is a janitor. For all x_13, x_13 will drink water or x_13 is a lawyer. There is at least one x_13 for which x_13 will take a plane.
There is at least one x_13 for which x_13 will not drink water can be inferred via the existential modus tollens rule. There is at least one x_13 for which x_13 will take a plane and x_13 is a janitor can be inferred via the existential conjunction rule. Some janitors will take a plane can be inferred via the existential conjunction rule.