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_5, x_5 will climb a mountain. For all x_5, if x_5 were sad, then x_5 is taking a plane. For all x_5, if x_5 works, then x_5 is sad. For all x_5, if x_5 climbs a mountain, then x_5 is working.
For all x_5, x_5 will work can be inferred via the universal modus ponens rule. For all x_5, if x_5 works, then x_5 is taking a plane can be inferred via the universal transitivity rule. For all x_5, if x_5 climbs a mountain, then x_5 is sad can be inferred via the universal transitivity rule.