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: q -> t. t -> s_2. u_1 -> q. s_2 -> u_1.
q -> s_2 can be inferred via the transitivity rule. t -> u_1 can be inferred via the transitivity rule. u_1 -> t can be inferred via the transitivity rule. s_2 -> q can be inferred via the transitivity rule.