devon energy corporation and subsidiaries notes to consolidated financial statements 2013 ( continued ) proved undeveloped reserves the following table presents the changes in devon 2019s total proved undeveloped reserves during 2012 ( in mmboe ) . .

U.S.
Canada
Total
Proved undeveloped reserves as of December 31, 2011
403
379
782
Extensions and discoveries
134
68
202
Revisions due to prices
(47)
9
(38)
Revisions other than price
(10)
(6)
(16)
Conversion to proved developed reserves
(73)
(17)
(90)
Proved undeveloped reserves as of December 31, 2012
407
433
840

at december 31 , 2012 , devon had 840 mmboe of proved undeveloped reserves .
this represents a 7 percent increase as compared to 2011 and represents 28 percent of its total proved reserves .
drilling and development activities increased devon 2019s proved undeveloped reserves 203 mmboe and resulted in the conversion of 90 mmboe , or 12 percent , of the 2011 proved undeveloped reserves to proved developed reserves .
costs incurred related to the development and conversion of devon 2019s proved undeveloped reserves were $ 1.3 billion for 2012 .
additionally , revisions other than price decreased devon 2019s proved undeveloped reserves 16 mmboe primarily due to its evaluation of certain u.s .
onshore dry-gas areas , which it does not expect to develop in the next five years .
the largest revisions relate to the dry-gas areas at carthage in east texas and the barnett shale in north texas .
a significant amount of devon 2019s proved undeveloped reserves at the end of 2012 largely related to its jackfish operations .
at december 31 , 2012 and 2011 , devon 2019s jackfish proved undeveloped reserves were 429 mmboe and 367 mmboe , respectively .
development schedules for the jackfish reserves are primarily controlled by the need to keep the processing plants at their 35000 barrel daily facility capacity .
processing plant capacity is controlled by factors such as total steam processing capacity , steam-oil ratios and air quality discharge permits .
as a result , these reserves are classified as proved undeveloped for more than five years .
currently , the development schedule for these reserves extends though the year 2031 .
price revisions 2012 - reserves decreased 171 mmboe primarily due to lower gas prices .
of this decrease , 100 mmboe related to the barnett shale and 25 mmboe related to the rocky mountain area .
2011 - reserves decreased 21 mmboe due to lower gas prices and higher oil prices .
the higher oil prices increased devon 2019s canadian royalty burden , which reduced devon 2019s oil reserves .
2010 - reserves increased 72 mmboe due to higher gas prices , partially offset by the effect of higher oil prices .
the higher oil prices increased devon 2019s canadian royalty burden , which reduced devon 2019s oil reserves .
of the 72 mmboe price revisions , 43 mmboe related to the barnett shale and 22 mmboe related to the rocky mountain area .
revisions other than price total revisions other than price for 2012 and 2011 primarily related to devon 2019s evaluation of certain dry gas regions noted in the proved undeveloped reserves discussion above .
total revisions other than price for 2010 primarily related to devon 2019s drilling and development in the barnett shale. .

Question: Analyse this data from a financial earnings document. what is the approximate total amount of proved reserves?
Choices:
-3000
-836.4
30
3.6
3000.0
Correct choice index: 4