Please answer the given financial question based on the context.
Context: supplementary information on oil and gas producing activities ( unaudited ) changes in the standardized measure of discounted future net cash flows ( in millions ) 2011 2010 2009 .
|( in millions )|2011|2010|2009|
|sales and transfers of oil and gas produced net of production and administrative costs|$ -7922 ( 7922 )|$ -6330 ( 6330 )|$ -4876 ( 4876 )|
|net changes in prices and production and administrative costs related to future production|12313|9843|4840|
|extensions discoveries and improved recovery less related costs|1454|1268|1399|
|development costs incurred during the period|1899|2546|2786|
|changes in estimated future development costs|-1349 ( 1349 )|-2153 ( 2153 )|-3773 ( 3773 )|
|revisions of previous quantity estimates|2526|1117|5110|
|net changes in purchases and sales of minerals in place|233|-20 ( 20 )|-159 ( 159 )|
|accretion of discount|2040|1335|787|
|net change in income taxes|-6676 ( 6676 )|-4231 ( 4231 )|-4345 ( 4345 )|
|timing and other|130|250|-149 ( 149 )|
|net change for the year|4648|3625|1620|
|beginning of the year|9280|5655|4035|
|end of year|$ 13928|$ 9280|$ 5655|
.
Question: what were total development costs in millions for the three year period?


Answer: The answer is:7231.0