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: w <-> u_1. ~w. u_1 or s_2.
w -> u_1 can be inferred via the biconditional elimination rule. u_1 -> w can be inferred via the biconditional elimination rule. ~u_1 can be inferred via the biconditional elimination rule.