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: r -> s. s_1 <-> s. ~s_1. p <-> r.
s_1 -> s can be inferred via the biconditional elimination rule. p -> r can be inferred via the biconditional elimination rule. s -> s_1 can be inferred via the biconditional elimination rule. r -> p can be inferred via the biconditional elimination rule. ~s can be inferred via the biconditional elimination rule.