Task: Table-QA (source dataset: FinQA)

Task: 
You are given a table containing structured data and a natural language question referring to the table. Your goal is to analyze the table and provide an accurate and concise answer based on the given data.

Instructions:
1. Understand the Table: Examine the structure, headers, and data in the table. Identify relevant columns and rows related to the question.
2. Interpret the Question: Determine whether the question requires direct retrieval, aggregation, comparison, sorting, filtering, or inference.
3. Extract the Answer: Use logical reasoning and numerical operations (if necessary) to derive the correct response from the table.
4. Format the Answer: No explanation, return the answer in a structured JSON format: {"answer": <answer>}. If the question cannot be answered due to missing or ambiguous data, return a JSON response with {"answer": null}.

Table:
| millions of dollars                   | 2007           | 2006           | 2005           |
|:--------------------------------------|:---------------|:---------------|:---------------|
| cash provided by operating activities | $ 3277         | $ 2880         | $ 2595         |
| cash used in investing activities     | -2426 ( 2426 ) | -2042 ( 2042 ) | -2047 ( 2047 ) |
| dividends paid                        | -364 ( 364 )   | -322 ( 322 )   | -314 ( 314 )   |
| free cash flow                        | $ 487          | $ 516          | $ 234          |

Question:
what was change in millions of free cash flow from 2005 to 2006?


pre_text: 2022 fuel prices 2013 crude oil prices increased at a steady rate in 2007 , rising from a low of $ 56.58 per barrel in january to close at nearly $ 96.00 per barrel at the end of december .
our 2007 average fuel price increased by 9% ( 9 % ) and added $ 242 million of operating expenses compared to 2006 .
our fuel surcharge programs are designed to help offset the impact of higher fuel prices .
in addition , our fuel conservation efforts allowed us to improve our consumption rate by 2% ( 2 % ) .
locomotive simulator training , operating practices , and technology all contributed to this improvement , saving approximately 21 million gallons of fuel in 2007 .
2022 free cash flow 2013 cash generated by operating activities totaled a record $ 3.3 billion , yielding free cash flow of $ 487 million in 2007 .
free cash flow is defined as cash provided by operating activities , less cash used in investing activities and dividends paid .
free cash flow is not considered a financial measure under accounting principles generally accepted in the united states ( gaap ) by sec regulation g and item 10 of sec regulation s-k .
we believe free cash flow is important in evaluating our financial performance and measures our ability to generate cash without additional external financings .
free cash flow should be considered in addition to , rather than as a substitute for , cash provided by operating activities .
the following table reconciles cash provided by operating activities ( gaap measure ) to free cash flow ( non-gaap measure ) : millions of dollars 2007 2006 2005 .
post_text: 2008 outlook 2022 safety 2013 operating a safe railroad benefits our employees , our customers , our shareholders , and the public .
we will continue using a multi-faceted approach to safety , utilizing technology , risk assessment , quality control , and training for , and engaging with our employees .
we plan to implement total safety culture ( tsc ) throughout our operations .
tsc , an employee-focused initiative that has helped improve safety , is a process designed to establish , maintain , and promote safety among co-workers .
with respect to public safety , we will continue our efforts to maintain , upgrade , and close crossings , install video cameras on locomotives , and educate the public about crossing safety through various internal and industry programs , along with other activities .
2022 commodity revenue 2013 despite uncertainty regarding the u.s .
economy , we expect record revenue in 2008 based on current economic indicators , forecasted demand , improved customer service , and additional opportunities to reprice certain of our business .
yield increases and fuel surcharges will be the primary drivers of commodity revenue growth in 2008 .
we expect that overall volume will fall within a range of 1% ( 1 % ) higher to 1% ( 1 % ) lower than 2007 , with continued softness in some market sectors .
2022 transportation plan 2013 in 2008 , we will continue to evaluate traffic flows and network logistic patterns to identify additional opportunities to simplify operations and improve network efficiency and asset utilization .
we plan to maintain adequate manpower and locomotives , improve productivity using industrial engineering techniques , and improve our operating margins .
2022 fuel prices 2013 fuel prices should remain volatile , with crude oil prices and conversion and regional spreads fluctuating throughout the year .
on average , we expect fuel prices to increase 15% ( 15 % ) to 20% ( 20 % ) above the average price in 2007 .
to reduce the impact of fuel price on earnings , we will continue to seek recovery from our customers through our fuel surcharge programs and expand our fuel conservation efforts. .
label: 282
qa: answer: 282
ann_table_rows: 4
steps: op: minus1-1
arg1: 516
arg2: 234
res: 282
program: subtract(516, 234)
gold_inds: table_4: millions of dollars the free cash flow of 2007 is $ 487 ; the free cash flow of 2006 is $ 516 ; the free cash flow of 2005 is $ 234 ;
exe_ans: 282
tfidftopn: text_10: the following table reconciles cash provided by operating activities ( gaap measure ) to free cash flow ( non-gaap measure ) : millions of dollars 2007 2006 2005 .
text_5: 2022 free cash flow 2013 cash generated by operating activities totaled a record $ 3.3 billion , yielding free cash flow of $ 487 million in 2007 .
program_re: subtract(516, 234)
model_input: table_1
millions of dollars the cash provided by operating activities of 2007 is $ 3277 ; the cash provided by operating activities of 2006 is $ 2880 ; the cash provided by operating activities of 2005 is $ 2595 ;
table_2
millions of dollars the cash used in investing activities of 2007 is -2426 ( 2426 ) ; the cash used in investing activities of 2006 is -2042 ( 2042 ) ; the cash used in investing activities of 2005 is -2047 ( 2047 ) ;
table_4
millions of dollars the free cash flow of 2007 is $ 487 ; the free cash flow of 2006 is $ 516 ; the free cash flow of 2005 is $ 234 ;