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 sad, then x_6 is sleeping. For all x_6, if x_6 were a bartender, then x_6 is sad. For all x_6, if x_6 sleeps, then x_6 is a politician. There is at least one x_6 for which if x_6 were a politician, then x_6 is an artist.
For all x_6, if x_6 were sad, then x_6 is a politician can be inferred via the universal transitivity rule. For all x_6, if x_6 were a bartender, then x_6 is sleeping can be inferred via the universal transitivity rule. There is at least one x_6 for which if x_6 sleeps, then x_6 is an artist can be inferred via the existential transitivity rule.