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_1 or ~q_1. p_9 <-> p_1.
q_1 -> p_1 can be inferred via the rewriting rule. p_9 -> p_1 can be inferred via the biconditional elimination rule. p_1 -> p_9 can be inferred via the biconditional elimination rule.