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