Grape Corporation is audited every year, and in preparation for this year's audit, Grapes tax advisor CPA firm discovers that Grape has been using an incorrect method of computing inventories for 20 years. It is more likely to be discovered in this year's audit, since the product line was discontinued. When the potential adjustment was computed, the CPA determined that Cost of Goods Sold had been overstated by a total of $400,000. What are Grapes options at this point ? Explain. (Hint:refer to Rev.Proc. 2015-13 & Rev.Proc 2015-14.)