Answer:
Retained earnings will be less by $13 million than actual retained earnings.
Explanation:
Since there is an error in depreciation as on December 31, 2018
Where it is overstated by $20 million, and therefore net retained earnings of the year 2018 will be understated as because of overstatement of expenses.
Net effect of taxes will be that, $20 million X 35% tax = $7 taxes saved.
Reduced balance of retained earnings by = $20 - $7 = $13 million.