{"pre_text": ["except for long-term debt , the carrying amounts of the company 2019s other financial instruments are measured at fair value or approximate fair value due to the short-term nature of these instruments .", "asset retirement obligations 2014the company records all known asset retirement obligations within other current liabilities for which the liability 2019s fair value can be reasonably estimated , including certain asbestos removal , asset decommissioning and contractual lease restoration obligations .", "the changes in the asset retirement obligation carrying amounts during 2011 , 2010 and 2009 were as follows : ( $ in millions ) retirement obligations ."], "post_text": ["the company also has known conditional asset retirement obligations related to assets currently in use , such as certain asbestos remediation and asset decommissioning activities to be performed in the future , that were not reasonably estimable as of december 31 , 2011 and 2010 , due to insufficient information about the timing and method of settlement of the obligation .", "accordingly , the fair value of these obligations has not been recorded in the consolidated financial statements .", "environmental remediation and/or asset decommissioning of the relevant facilities may be required when the company ceases to utilize these facilities .", "in addition , there may be conditional environmental asset retirement obligations that the company has not yet discovered .", "income taxes 2014income tax expense and other income tax related information contained in the financial statements for periods before the spin-off are presented as if the company filed its own tax returns on a stand-alone basis , while similar information for periods after the spin-off reflect the company 2019s positions to be filed in its own tax returns in the future .", "income tax expense and other related information are based on the prevailing statutory rates for u.s .", "federal income taxes and the composite state income tax rate for the company for each period presented .", "state and local income and franchise tax provisions are allocable to contracts in process and , accordingly , are included in general and administrative expenses .", "deferred income taxes are recorded when revenues and expenses are recognized in different periods for financial statement purposes than for tax return purposes .", "deferred tax asset or liability account balances are calculated at the balance sheet date using current tax laws and rates in effect .", "determinations of the expected realizability of deferred tax assets and the need for any valuation allowances against these deferred tax assets were evaluated based upon the stand-alone tax attributes of the company , and an $ 18 million valuation allowance was deemed necessary as of december 31 , 2011 .", "no valuation allowance was deemed necessary as of december 31 , 2010 .", "uncertain tax positions meeting the more-likely-than-not recognition threshold , based on the merits of the position , are recognized in the financial statements .", "we recognize the amount of tax benefit that is greater than 50% ( 50 % ) likely to be realized upon ultimate settlement with the related tax authority .", "if a tax position does not meet the minimum statutory threshold to avoid payment of penalties , we recognize an expense for the amount of the penalty in the period the tax position is claimed or expected to be claimed in our tax return .", "penalties , if probable and reasonably estimable , are recognized as a component of income tax expense .", "we also recognize accrued interest related to uncertain tax positions in income tax expense .", "the timing and amount of accrued interest is determined by the applicable tax law associated with an underpayment of income taxes .", "see note 12 : income taxes .", "under existing gaap , changes in accruals associated with uncertainties are recorded in earnings in the period they are determined. ."], "table": [["( $ in millions )", "asset retirement obligations"], ["balance at january 1 2009", "$ 3"], ["accretion expense", "0"], ["payment of asset retirement obligation", "0"], ["balance at december 31 2009", "3"], ["obligation relating to the future retirement of a facility", "17"], ["accretion expense", "0"], ["payment of asset retirement obligation", "0"], ["balance at december 31 2010", "20"], ["obligation relating to the future retirement of a facility", "5"], ["accretion expense", "0"], ["payment of asset retirement obligation", "0"], ["balance at december 31 2011", "$ 25"]], "table_ori": [["($ in millions)", "Asset Retirement Obligations"], ["Balance at January 1, 2009", "$3"], ["Accretion expense", "0"], ["Payment of asset retirement obligation", "0"], ["Balance at December 31, 2009", "3"], ["Obligation relating to the future retirement of a facility", "17"], ["Accretion expense", "0"], ["Payment of asset retirement obligation", "0"], ["Balance at December 31, 2010", "20"], ["Obligation relating to the future retirement of a facility", "5"], ["Accretion expense", "0"], ["Payment of asset retirement obligation", "0"], ["Balance at December 31, 2011", "$25"]]}

Question: what was the net increase in aro during the period , in millions?
Evidence:
table_1: ( $ in millions ) the balance at january 1 2009 of asset retirement obligations is $ 3 ;
table_12: ( $ in millions ) the balance at december 31 2011 of asset retirement obligations is $ 25 ;
Program: subtract(25, 3)
Answer:
str_answer: 22
exe_answer: 22