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_4. q_4 <-> q_3. q_4 -> r_4. p <-> q_3.
~q_4 can be inferred via the modus tollens rule. q_4 -> q_3 can be inferred via the biconditional elimination rule. p -> q_3 can be inferred via the biconditional elimination rule. q_3 -> q_4 can be inferred via the biconditional elimination rule. q_3 -> p can be inferred via the biconditional elimination rule.