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 -> q_6. q_6 -> t. t or r. r -> q_6.
r -> t can be inferred via the transitivity rule. q_6 can be inferred via the disjunction elimination rule. t <-> q_6 can be inferred via the biconditional introduction rule. q_6 <-> t can be inferred via the biconditional introduction rule.