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: ~u_1. t <-> u_1. s -> ~r_3. t or r_3.
t -> u_1 can be inferred via the biconditional elimination rule. u_1 -> t can be inferred via the biconditional elimination rule. ~t can be inferred via the biconditional elimination rule.