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_4. u_4 -> p_17. p_17 <-> q_17. q_17 or ~t.
p_17 can be inferred via the modus ponens rule. t -> q_17 can be inferred via the rewriting rule. p_17 -> q_17 can be inferred via the biconditional elimination rule. q_17 -> p_17 can be inferred via the biconditional elimination rule.