{"pre_text": ["debt maturities 2013 the following table presents aggregate debt maturities as of december 31 , 2011 , excluding market value adjustments : millions ."], "post_text": ["as of both december 31 , 2011 and december 31 , 2010 , we have reclassified as long-term debt approximately $ 100 million of debt due within one year that we intend to refinance .", "this reclassification reflects our ability and intent to refinance any short-term borrowings and certain current maturities of long- term debt on a long-term basis .", "mortgaged properties 2013 equipment with a carrying value of approximately $ 2.9 billion and $ 3.2 billion at december 31 , 2011 and 2010 , respectively , served as collateral for capital leases and other types of equipment obligations in accordance with the secured financing arrangements utilized to acquire such railroad equipment .", "as a result of the merger of missouri pacific railroad company ( mprr ) with and into uprr on january 1 , 1997 , and pursuant to the underlying indentures for the mprr mortgage bonds , uprr must maintain the same value of assets after the merger in order to comply with the security requirements of the mortgage bonds .", "as of the merger date , the value of the mprr assets that secured the mortgage bonds was approximately $ 6.0 billion .", "in accordance with the terms of the indentures , this collateral value must be maintained during the entire term of the mortgage bonds irrespective of the outstanding balance of such bonds .", "credit facilities 2013 during the second quarter of 2011 , we replaced our $ 1.9 billion revolving credit facility , which was scheduled to expire in april 2012 , with a new $ 1.8 billion facility that expires in may 2015 ( the facility ) .", "the facility is based on substantially similar terms as those in the previous credit facility .", "on december 31 , 2011 , we had $ 1.8 billion of credit available under the facility , which is designated for general corporate purposes and supports the issuance of commercial paper .", "we did not draw on either facility during 2011 .", "commitment fees and interest rates payable under the facility are similar to fees and rates available to comparably rated , investment-grade borrowers .", "the facility allows for borrowings at floating rates based on london interbank offered rates , plus a spread , depending upon our senior unsecured debt ratings .", "the facility requires the corporation to maintain a debt-to-net-worth coverage ratio as a condition to making a borrowing .", "at december 31 , 2011 , and december 31 , 2010 ( and at all times during the year ) , we were in compliance with this covenant .", "the definition of debt used for purposes of calculating the debt-to-net-worth coverage ratio includes , among other things , certain credit arrangements , capital leases , guarantees and unfunded and vested pension benefits under title iv of erisa .", "at december 31 , 2011 , the debt-to-net-worth coverage ratio allowed us to carry up to $ 37.2 billion of debt ( as defined in the facility ) , and we had $ 9.5 billion of debt ( as defined in the facility ) outstanding at that date .", "under our current capital plans , we expect to continue to satisfy the debt-to-net-worth coverage ratio ; however , many factors beyond our reasonable control ( including the risk factors in item 1a of this report ) could affect our ability to comply with this provision in the future .", "the facility does not include any other financial restrictions , credit rating triggers ( other than rating-dependent pricing ) , or any other provision that could require us to post collateral .", "the facility also includes a $ 75 million cross-default provision and a change-of-control provision .", "during 2011 , we did not issue or repay any commercial paper and , at december 31 , 2011 , we had no commercial paper outstanding .", "outstanding commercial paper balances are supported by our revolving credit facility but do not reduce the amount of borrowings available under the facility .", "dividend restrictions 2013 our revolving credit facility includes a debt-to-net worth covenant ( discussed in the credit facilities section above ) that , under certain circumstances , restricts the payment of cash ."], "table": [["2012", "$ 309"], ["2013", "636"], ["2014", "706"], ["2015", "467"], ["2016", "517"], ["thereafter", "6271"], ["total debt", "$ 8906"]], "table_ori": [["2012", "$309"], ["2013", "636"], ["2014", "706"], ["2015", "467"], ["2016", "517"], ["Thereafter", "6,271"], ["Total debt", "$8,906"]]}

Question: at december 31 , 2011 , what is the additional borrowing capacity in billions pursuant to the current debt coverage restrictions?
Evidence:
text_16: at december 31 , 2011 , the debt-to-net-worth coverage ratio allowed us to carry up to $ 37.2 billion of debt ( as defined in the facility ) , and we had $ 9.5 billion of debt ( as defined in the facility ) outstanding at that date .
Program: subtract(37.2, 9.5)
Answer:
str_answer: 27.7
exe_answer: 27.7