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: p_3 <-> u_3. p_3 or s_1. s_1 <-> u_3.
p_3 -> u_3 can be inferred via the biconditional elimination rule. s_1 -> u_3 can be inferred via the biconditional elimination rule. u_3 -> p_3 can be inferred via the biconditional elimination rule. u_3 -> s_1 can be inferred via the biconditional elimination rule.