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_8, x_8 will play tennis. For all x_8, if x_8 climbs a mountain, then x_8 is taking a plane. For all x_8, x_8 will not take a plane. For all x_8, x_8 will climb a mountain or x_8 is happy.
For all x_8, x_8 will not climb a mountain can be inferred via the universal modus tollens rule.