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_4 <-> t. r_3 or t. s_4 or ~r_3.
r_3 -> s_4 can be inferred via the rewriting rule. s_4 -> t can be inferred via the biconditional elimination rule. t -> s_4 can be inferred via the biconditional elimination rule.