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: r -> t. s_2. s_2 -> t. u_4 -> s_2. t -> u_4.
t can be inferred via the modus ponens rule. r -> u_4 can be inferred via the transitivity rule. s_2 -> u_4 can be inferred via the transitivity rule. u_4 -> t can be inferred via the transitivity rule. t -> s_2 can be inferred via the transitivity rule.