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: There is at least one x_2 for which if x_2 were sad, then x_2 is rich. For all x_2, x_2 is not rich. For all x_2, if x_2 were a scientist, then x_2 is sad.
There is at least one x_2 for which x_2 is not sad can be inferred via the existential modus tollens rule. There is at least one x_2 for which if x_2 were a scientist, then x_2 is rich can be inferred via the existential transitivity rule.