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: s <-> q. p -> q_1. q_1 -> q.
p -> q can be inferred via the transitivity rule. s -> q can be inferred via the biconditional elimination rule. q -> s can be inferred via the biconditional elimination rule.