Snoopy Inc. acquired a packaging machine from Red Barron Corporation. Red Barron completed construction of the machine on January 1, 2019. In payment for the machine Snoopy issued a three-year installment note to be paid in three equal payments at the end of each year. The payments include interest at the rate of 15%. Red Barron made a conceptual error in preparing the amortization schedule, which Snoopy failed to discover until 2021. As a result of the error, Snoopy understated interest expense by $50,000 in 2019 and $45,000 in 2020. Snoopy should account for the error: O Prospectively. O No adjustment is needed. O Retrospectively. O None of the options listed.