pre_text: other income increased in 2011 versus 2010 due to higher gains from real estate sales , lower environmental costs associated with non-operating properties and the comparative impact of premiums paid for early redemption of long-term debt in the first quarter of 2010 . interest expense 2013 interest expense decreased in 2012 versus 2011 reflecting a lower effective interest rate in 2012 of 6.0% ( 6.0 % ) versus 6.2% ( 6.2 % ) in 2011 as the debt level did not materially change in 2012 . interest expense decreased in 2011 versus 2010 due to a lower weighted-average debt level of $ 9.2 billion versus $ 9.7 billion . the effective interest rate was 6.2% ( 6.2 % ) in both 2011 and 2010 . income taxes 2013 higher pre-tax income increased income taxes in 2012 compared to 2011 . our effective tax rate for 2012 was relatively flat at 37.6% ( 37.6 % ) compared to 37.5% ( 37.5 % ) in 2011 . income taxes were higher in 2011 compared to 2010 , primarily driven by higher pre-tax income . our effective tax rate remained relatively flat at 37.5% ( 37.5 % ) in 2011 compared to 37.3% ( 37.3 % ) in 2010 . other operating/performance and financial statistics we report key performance measures weekly to the association of american railroads ( aar ) , including carloads , average daily inventory of freight cars on our system , average train speed , and average terminal dwell time . we provide this data on our website at www.up.com/investors/reports/index.shtml . operating/performance statistics railroad performance measures reported to the aar , as well as other performance measures , are included in the table below : 2012 2011 2010 % (  % ) change 2012 v 2011 % (  % ) change 2011 v 2010 .
post_text: average train speed 2013 average train speed is calculated by dividing train miles by hours operated on our main lines between terminals . average train speed , as reported to the association of american railroads ( aar ) , increased 4% ( 4 % ) in 2012 versus 2011 . efficient operations and relatively mild weather conditions during the year compared favorably to 2011 , during which severe winter weather , flooding , and extreme heat and drought affected various parts of our network . we continued operating a fluid and efficient network while handling essentially the same volume and adjusting operations to accommodate increased capital project work on our network compared to 2011 . the extreme weather challenges in addition to increased carloadings and traffic mix changes , led to a 2% ( 2 % ) decrease in average train speed in 2011 compared to 2010 . average terminal dwell time 2013 average terminal dwell time is the average time that a rail car spends at our terminals . lower average terminal dwell time improves asset utilization and service . average terminal dwell time remained flat in 2012 compared to 2011 , despite a shift in traffic mix to more manifest shipments , which require more switching at terminals . average terminal dwell time increased 3% ( 3 % ) in 2011 compared to 2010 . additional volume , weather challenges , track replacement programs , and a shift of traffic mix to more manifest shipments , which require additional terminal processing , all contributed to the increase . average rail car inventory 2013 average rail car inventory is the daily average number of rail cars on our lines , including rail cars in storage . lower average rail car inventory reduces congestion in our yards and sidings , which increases train speed , reduces average terminal dwell time , and improves rail car utilization . despite a shift in traffic mix from coal to shale-related and automotive shipments with longer .
table: <i>2012</i> <i>2011</i> <i>2010</i> <i>% Change 2012 v 2011</i> <i>% Change 2011 v 2010</i>
table: Average train speed (miles per hour) 26.5 25.6 26.2 4 % (2)%
table: Average terminal dwell time (hours) 26.2 26.2 25.4 - % 3 %
table: Average rail car inventory (thousands) 269.1 272.9 274.4 (1)% (1)%
table: Gross ton-miles (billions) 959.3 978.2 931.4 (2)% 5 %
table: Revenue ton-miles (billions) 521.1 544.4 520.4 (4)% 5 %
table: Operating ratio 67.8 70.7 70.6 (2.9)pts 0.1 pts
table: Employees (average) 45,928 44,861 42,884 2 % 5 %
table: Customer satisfaction index 93 92 89 1 pt 3 pts
question: Analyse this data from a financial earnings document. what is the 2011 total interest expense in billions based on the weighted-average debt level and effective interest rate?