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_6 -> p_13. p_13 <-> s_1. p_6 or s_1.
p_13 -> s_1 can be inferred via the biconditional elimination rule. s_1 -> p_13 can be inferred via the biconditional elimination rule.