at december 31 , 2013 , total future minimum commitments under existing non-cancelable operating leases and purchase obligations were as follows: .
in 2015 what percentage of at december 31 , 2013 , total future minimum commitments under existing non-cancelable operating leases and purchase obligations is due to purchase obligations?
( a ) includes $ 3.3 billion relating to fiber supply agreements entered into at the time of the company 2019s 2006 transformation plan forestland sales and in conjunction with the 2008 acquisition of weyerhaeuser company 2019s containerboard , packaging and recycling business . rent expense was $ 215 million , $ 231 million and $ 205 million for 2013 , 2012 and 2011 , respectively . guarantees in connection with sales of businesses , property , equipment , forestlands and other assets , international paper commonly makes representations and warranties relating to such businesses or assets , and may agree to indemnify buyers with respect to tax and environmental liabilities , breaches of representations and warranties , and other matters . where liabilities for such matters are determined to be probable and subject to reasonable estimation , accrued liabilities are recorded at the time of sale as a cost of the transaction . environmental proceedings international paper has been named as a potentially responsible party in environmental remediation actions under various federal and state laws , including the comprehensive environmental response , compensation and liability act ( cercla ) . many of these proceedings involve the cleanup of hazardous substances at large commercial landfills that received waste from many different sources . while joint and several liability is authorized under cercla and equivalent state laws , as a practical matter , liability for cercla cleanups is typically allocated among the many potential responsible parties . remedial costs are recorded in the consolidated financial statements when they become probable and reasonably estimable . international paper has estimated the probable liability associated with these matters to be approximately $ 94 million in the aggregate at december 31 , 2013 . cass lake : one of the matters referenced above is a closed wood treating facility located in cass lake , minnesota . during 2009 , in connection with an environmental site remediation action under cercla , international paper submitted to the epa a site remediation feasibility study . in june 2011 , the epa selected and published a proposed soil remedy at the site with an estimated cost of $ 46 million . the overall remediation reserve for the site is currently $ 51 million to address this selection of an alternative for the soil remediation component of the overall site remedy . in october 2011 , the epa released a public statement indicating that the final soil remedy decision would be delayed . in the unlikely event that the epa changes its proposed soil remedy and approves instead a more expensive clean-up alternative , the remediation costs could be material , and significantly higher than amounts currently recorded . in october 2012 , the natural resource trustees for this site provided notice to international paper and other potentially responsible parties of their intent to perform a natural resource damage assessment . it is premature to predict the outcome of the assessment or to estimate a loss or range of loss , if any , which may be incurred . other : in addition to the above matters , other remediation costs typically associated with the cleanup of hazardous substances at the company 2019s current , closed or formerly-owned facilities , and recorded as liabilities in the balance sheet , totaled approximately $ 42 million at december 31 , 2013 . other than as described above , completion of required remedial actions is not expected to have a material effect on our consolidated financial statements . kalamazoo river : the company is a potentially responsible party with respect to the allied paper , inc./ portage creek/kalamazoo river superfund site ( kalamazoo river superfund site ) in michigan . the epa asserts that the site is contaminated primarily by pcbs as a result of discharges from various paper mills located along the kalamazoo river , including a paper mill formerly owned by st . regis paper company ( st . regis ) . the company is a successor in interest to st . regis . the company has not received any orders from the epa with respect to the site and continues to collect information from the epa and other parties relative to the site to evaluate the extent of its liability , if any , with respect to the site . accordingly , it is premature to estimate a loss or range of loss with respect to this site . also in connection with the kalamazoo river superfund site , the company was named as a defendant by georgia-pacific consumer products lp , fort james corporation and georgia pacific llc in a contribution and cost recovery action for alleged pollution at the site . the suit seeks contribution under cercla for $ 79 million in costs purportedly expended by plaintiffs as of the filing of the complaint and for future remediation costs . the suit alleges that a mill , during the time it was allegedly owned and operated by st . regis , discharged pcb contaminated solids and paper residuals resulting from paper de-inking and recycling . also named as defendants in the suit are ncr corporation and weyerhaeuser company . in mid-2011 , the suit was transferred from the district court for the eastern district of wisconsin to the district court for the western .