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: t <-> u_2. ~q_9. t or u. u_2 <-> q_9.
t -> u_2 can be inferred via the biconditional elimination rule. u_2 -> q_9 can be inferred via the biconditional elimination rule. u_2 -> t can be inferred via the biconditional elimination rule. q_9 -> u_2 can be inferred via the biconditional elimination rule. ~u_2 can be inferred via the biconditional elimination rule.