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_2. r_2 <-> q_7. q_15 -> w_4. p or q_15. p -> w_4.
w_4 can be inferred via the disjunction elimination rule. r_2 -> q_7 can be inferred via the biconditional elimination rule. q_7 -> r_2 can be inferred via the biconditional elimination rule. ~q_7 can be inferred via the biconditional elimination rule.