amount of commitment expiration per period other commercial commitments after millions total 2012 2013 2014 2015 2016 2016 .
[['other commercial commitmentsmillions', 'total', 'amount of commitment expiration per period 2012', 'amount of commitment expiration per period 2013', 'amount of commitment expiration per period 2014', 'amount of commitment expiration per period 2015', 'amount of commitment expiration per period 2016', 'amount of commitment expiration per period after 2016'], ['credit facilities [a]', '$ 1800', '$ -', '$ -', '$ -', '$ 1800', '$ -', '$ -'], ['receivables securitization facility [b]', '600', '600', '-', '-', '-', '-', '-'], ['guarantees [c]', '325', '18', '8', '214', '12', '13', '60'], ['standby letters of credit [d]', '24', '24', '-', '-', '-', '-', '-'], ['total commercialcommitments', '$ 2749', '$ 642', '$ 8', '$ 214', '$ 1812', '$ 13', '$ 60']]
[a] none of the credit facility was used as of december 31 , 2011 .[b] $ 100 million of the receivables securitization facility was utilized at december 31 , 2011 , which is accounted for as debt .the full program matures in august 2012 .[c] includes guaranteed obligations related to our headquarters building , equipment financings , and affiliated operations .[d] none of the letters of credit were drawn upon as of december 31 , 2011 .off-balance sheet arrangements guarantees 2013 at december 31 , 2011 , we were contingently liable for $ 325 million in guarantees .we have recorded a liability of $ 3 million for the fair value of these obligations as of december 31 , 2011 and 2010 .we entered into these contingent guarantees in the normal course of business , and they include guaranteed obligations related to our headquarters building , equipment financings , and affiliated operations .the final guarantee expires in 2022 .we are not aware of any existing event of default that would require us to satisfy these guarantees .we do not expect that these guarantees will have a material adverse effect on our consolidated financial condition , results of operations , or liquidity .other matters labor agreements 2013 in january 2010 , the nation 2019s largest freight railroads began the current round of negotiations with the labor unions .generally , contract negotiations with the various unions take place over an extended period of time .this round of negotiations was no exception .in september 2011 , the rail industry reached agreements with the united transportation union .on november 5 , 2011 , a presidential emergency board ( peb ) appointed by president obama issued recommendations to resolve the disputes between the u.s .railroads and 11 unions that had not yet reached agreements .since then , ten unions reached agreements with the railroads , all of them generally patterned on the recommendations of the peb , and the unions subsequently ratified these agreements .the railroad industry reached a tentative agreement with the brotherhood of maintenance of way employees ( bmwe ) on february 2 , 2012 , eliminating the immediate threat of a national rail strike .the bmwe now will commence ratification of this tentative agreement by its members .inflation 2013 long periods of inflation significantly increase asset replacement costs for capital-intensive companies .as a result , assuming that we replace all operating assets at current price levels , depreciation charges ( on an inflation-adjusted basis ) would be substantially greater than historically reported amounts .derivative financial instruments 2013 we may use derivative financial instruments in limited instances to assist in managing our overall exposure to fluctuations in interest rates and fuel prices .we are not a party to leveraged derivatives and , by policy , do not use derivative financial instruments for speculative purposes .derivative financial instruments qualifying for hedge accounting must maintain a specified level of effectiveness between the hedging instrument and the item being hedged , both at inception and throughout the hedged period .we formally document the nature and relationships between the hedging instruments and hedged items at inception , as well as our risk-management objectives , strategies for undertaking the various hedge transactions , and method of assessing hedge effectiveness .changes in the fair market value of derivative financial instruments that do not qualify for hedge accounting are charged to earnings .we may use swaps , collars , futures , and/or forward contracts to mitigate the risk of adverse movements in interest rates and fuel prices ; however , the use of these derivative financial instruments may limit future benefits from favorable price movements. .

Question: what percent of total commercial commitments are receivables securitization facility?
Answer: 22%