that nominal annual percentage rate which will yield a sum equal to the amount of the finance charge when it is applied to the unpaid balances of the amount financed, calculated according to the actuarial method of allocating payments made on a debt between the amount financed and the amount of the finance charge, pursuant to which a payment is applied first to the accumulated finance charge and the balance is applied to the unpaid amount financed; or

the rate determined by any method prescribed by the Bureau as a method which materially simplifies computation while retaining reasonable accuracy as compared with the rate determined under subparagraph (A).^[1]