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 or ~p_4. q <-> p_4.
p_4 -> q can be inferred via the rewriting rule. q -> p_4 can be inferred via the biconditional elimination rule. p_4 -> q can be inferred via the biconditional elimination rule.