Black, Inc. is a calendar-year corporation whose financial statements for 2017 and 2018 included errors as follows: Year Ending Inventory Depreciation Expense 2017 $324,000 overstated $270,000 overstated 2018 128,000 understated 90,000 understated Assume that purchases were recorded correctly and that no correcting entries were made at December 31, 2017, or at December 31, 2018. Ignoring income taxes, by how much should Black's retained earnings be retroactively adjusted at January 1, 2019?