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_6, if x_6 goes running, then x_6 is not climbing a mountain. For all x_6, x_6 will climb a mountain. For all x_6, x_6 will go running or x_6 will write a letter.
For all x_6, x_6 will not go running can be inferred via the universal modus tollens rule.