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_1. s_1 <-> q. s_1 -> s. q_1 <-> s.
s_1 -> q can be inferred via the biconditional elimination rule. q_1 -> s can be inferred via the biconditional elimination rule. q -> s_1 can be inferred via the biconditional elimination rule. s -> q_1 can be inferred via the biconditional elimination rule. ~s can be inferred via the biconditional elimination rule.