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_4 -> r_1. p_8 <-> s_4. w_4 -> p_8.
p_8 -> s_4 can be inferred via the biconditional elimination rule. s_4 -> p_8 can be inferred via the biconditional elimination rule.