at december 31 , 2014 , total future minimum commitments under existing non-cancelable operating leases and purchase obligations were as follows: .

2015: lease obligations: 142
purchase obligations ( a ): 3266
total: 3408
2016: lease obligations: 106
purchase obligations ( a ): 761
total: 867
2017: lease obligations: 84
purchase obligations ( a ): 583
total: 667
2018: lease obligations: 63
purchase obligations ( a ): 463
total: 526
2019: lease obligations: 45
purchase obligations ( a ): 422
total: 467
thereafter: lease obligations: 91
purchase obligations ( a ): 1690
total: 1781

( a ) includes $ 2.3 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 $ 154 million , $ 168 million and $ 185 million for 2014 , 2013 and 2012 , 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 cercla and state actions 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 $ 95 million in the aggregate as of december 31 , 2014 . 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 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 $ 50 million to address the 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 remediation costs 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 $ 41 million as of december 31 , 2014 . other than as described above , completion of required remedial actions is not expected to have a material effect on our consolidated financial statements . legal proceedings environmental 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 . although the company has not received any orders from the epa , in december 2014 , the epa sent the company a letter demanding payment of $ 19 million to reimburse the epa for costs associated with a time critical removal action of pcb contaminated sediments from a portion of the site . the company 2019s cercla liability has not been finally determined with respect to this or any other portion of the site and we have declined to reimburse the epa at this time . as noted below , the company is involved in allocation/ apportionment litigation with regard to the site . accordingly , it is premature to estimate a loss or range of loss with respect to this 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 .

Questions:
what was the rent expense in 2014?
what was it in 2013?
what is the sum
what is the total sum including 2012?

Answers:
154
168
322
507