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 or r_2. s_4 <-> t_4. ~q or w. ~t_4.
s_4 -> t_4 can be inferred via the biconditional elimination rule. t_4 -> s_4 can be inferred via the biconditional elimination rule. ~s_4 can be inferred via the biconditional elimination rule.