table of contents respect to the mainline american and the mainline us airways dispatchers , flight simulator engineers and flight crew training instructors , all of whom are now represented by the twu , a rival organization , the national association of airline professionals ( naap ) , filed single carrier applications seeking to represent those employees .
the nmb will have to determine that a single transportation system exists and will certify a post-merger representative of the combined employee groups before the process for negotiating new jcbas can begin .
the merger had no impact on the cbas that cover the employees of our wholly-owned subsidiary airlines which are not being merged ( envoy , piedmont and psa ) .
for those employees , the rla provides that cbas do not expire , but instead become amendable as of a stated date .
in 2014 , envoy pilots ratified a new 10 year collective bargaining agreement , piedmont pilots ratified a new 10 year collective bargaining agreement and piedmont flight attendants ratified a new five-year collective bargaining agreement .
with the exception of the passenger service employees who are now engaged in traditional rla negotiations that are expected to result in a jcba and the us airways flight simulator engineers and flight crew training instructors , other union-represented american mainline employees are covered by agreements that are not currently amendable .
until those agreements become amendable , negotiations for jcbas will be conducted outside the traditional rla bargaining process described above , and , in the meantime , no self-help will be permissible .
the piedmont mechanics and stock clerks and the psa and piedmont dispatchers also have agreements that are now amendable and are engaged in traditional rla negotiations .
none of the unions representing our employees presently may lawfully engage in concerted refusals to work , such as strikes , slow-downs , sick-outs or other similar activity , against us .
nonetheless , there is a risk that disgruntled employees , either with or without union involvement , could engage in one or more concerted refusals to work that could individually or collectively harm the operation of our airline and impair our financial performance .
for more discussion , see part i , item 1a .
risk factors 2013 201cunion disputes , employee strikes and other labor-related disruptions may adversely affect our operations . 201d aircraft fuel our operations and financial results are significantly affected by the availability and price of jet fuel .
based on our 2015 forecasted mainline and regional fuel consumption , we estimate that , as of december 31 , 2014 , a one cent per gallon increase in aviation fuel price would increase our 2015 annual fuel expense by $ 43 million .
the following table shows annual aircraft fuel consumption and costs , including taxes , for our mainline operations for 2012 through 2014 ( gallons and aircraft fuel expense in millions ) .
year gallons average price per gallon aircraft fuel expense percent of total mainline operating expenses .

Year
Gallons
Average Price per Gallon
Aircraft Fuel Expense
Percent of Total Mainline Operating Expenses
2014
3,644
$2.91
$10,592
33.2%
2013 (a)
3,608
3.08
11,109
35.4
2012 (a)
3,512
3.19
11,194
35.8

( a ) represents 201ccombined 201d financial data , which includes the financial results of american and us airways group each on a standalone basis .
total combined fuel expenses for our wholly-owned and third-party regional carriers operating under capacity purchase agreements of american and us airways group , each on a standalone basis , were $ 2.0 billion , $ 2.1 billion and $ 2.1 billion for the years ended december 31 , 2014 , 2013 and 2012 , respectively. .

Question: Analyse this data from a financial earnings document. what were total mainline operating expenses in 2013?
Choices:
0.00319
316.21469
-313.81356
313.81356
315.81356
Correct choice index: 3