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: p_9 or ~s_1. s_1 or q_1. p_9 <-> q_1.
s_1 -> p_9 can be inferred via the rewriting rule. p_9 -> q_1 can be inferred via the biconditional elimination rule. q_1 -> p_9 can be inferred via the biconditional elimination rule.