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, if x_8 goes running, then x_8 is climbing a mountain. There is at least one x_8 for which x_8 will climb a mountain if and only if x_8 will go running. For all x_8, if x_8 climbs a mountain, then x_8 is happy. For all x_8, x_8 is not happy.
For all x_8, x_8 will not climb a mountain can be inferred via the universal modus tollens rule. For all x_8, if x_8 goes running, then x_8 is happy can be inferred via the universal transitivity rule. There is at least one x_8 for which if x_8 climbs a mountain, then x_8 is running can be inferred via the existential biconditional elimination rule. There is at least one x_8 for which if x_8 goes running, then x_8 is climbing a mountain can be inferred via the existential biconditional elimination rule.