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: forall x_17: U(x_17) -> S_17(x_17). t_1 -> U(a_17). S_17(a_17) -> t_1. S_17(a_17).
S_17(a_17) -> U(a_17) can be inferred via the transitivity rule. exists x: S_17(x) can be inferred via the existential generalization rule.