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_1, if x_1 were sad, then x_1 is making tea. There is at least one x_1 for which if x_1 were a taxi driver, then x_1 is rich. For all x_1, if x_1 were rich, then x_1 is sad.
For all x_1, if x_1 were rich, then x_1 is making tea can be inferred via the universal transitivity rule. There is at least one x_1 for which if x_1 were a taxi driver, then x_1 is sad can be inferred via the existential transitivity rule.