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 -> p_15. p_15 -> s. s.
p_15 can be inferred via the modus ponens rule. s <-> p_15 can be inferred via the biconditional introduction rule. p_15 <-> s can be inferred via the biconditional introduction rule.