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: q_6 -> u_2. u_2 -> q_6. q_6.
u_2 can be inferred via the modus ponens rule. q_6 <-> u_2 can be inferred via the biconditional introduction rule. u_2 <-> q_6 can be inferred via the biconditional introduction rule.