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: ~s. q -> r_2. t_1 -> q. r_2 <-> s.
t_1 -> r_2 can be inferred via the transitivity rule. r_2 -> s can be inferred via the biconditional elimination rule. s -> r_2 can be inferred via the biconditional elimination rule. ~r_2 can be inferred via the biconditional elimination rule.