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 were fast, then x_6 is sad. For all x_6, if x_6 climbs a mountain, then x_6 is fast. There is at least one x_6 for which if x_6 were an astronaut, then x_6 is climbing a mountain. For all x_6, if x_6 were sad, then x_6 is sleeping.
For all x_6, if x_6 were fast, then x_6 is sleeping can be inferred via the universal transitivity rule. For all x_6, if x_6 climbs a mountain, then x_6 is sad can be inferred via the universal transitivity rule. There is at least one x_6 for which if x_6 were an astronaut, then x_6 is fast can be inferred via the existential transitivity rule.