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 <-> w. r_1 -> w. q_2 -> r_1. q_2.
r_1 can be inferred via the modus ponens rule. q_2 -> w can be inferred via the transitivity rule. p_9 -> w can be inferred via the biconditional elimination rule. w -> p_9 can be inferred via the biconditional elimination rule.