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_1 <-> s. ~s. p_1 -> s_1. s_1 -> p_1.
p_1 <-> s_1 can be inferred via the biconditional introduction rule. s_1 <-> p_1 can be inferred via the biconditional introduction rule. s_1 -> s can be inferred via the biconditional elimination rule. s -> s_1 can be inferred via the biconditional elimination rule. ~s_1 can be inferred via the biconditional elimination rule.