Webster Products, Inc., adopted the dollar-value LIFO method of determining inventory costs for financial and income tax reporting on January 1, 2021. Webster continues to use the FIFO method for internal decision-making purposes. Webster's FIFO inventories at December 31,2021,2022, and 2023 , were $300,000,$412,500, and $585,000, respectively. Internally generated cost indexes are used to convert FIFO inventory amounts to dollar-value LIFO amounts. Webster estimated these indexes as follows: Required: 1. Determine Webster's dollar-value LIFO inventory at December 31,2022 and 2023. 2. Will Webster account for the change (a) retrospectively or (b) prospectively