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:
|   Unnamed: 0 | amount   |
|-------------:|:---------|
|         2019 | $ 15     |
|         2020 | 13       |
|         2021 | 11       |
|         2022 | 10       |
|         2023 | 7        |

Question:
what is total intangible asset amortization expense ( millions ) for the years ended december 31 , 2018 , 2017 and 2016?


pre_text: intangible asset amortization expense amounted to $ 12 million , $ 4 million and $ 4 million for the years ended december 31 , 2018 , 2017 and 2016 , respectively .
estimated amortization expense for the next five years subsequent to december 31 , 2018 is as follows: .
post_text: note 9 : shareholders 2019 equity common stock under the dividend reinvestment and direct stock purchase plan ( the 201cdrip 201d ) , shareholders may reinvest cash dividends and purchase additional company common stock , up to certain limits , through the plan administrator without commission fees .
shares purchased by participants through the drip may be newly issued shares , treasury shares , or at the company 2019s election , shares purchased by the plan administrator in the open market or in privately negotiated transactions .
purchases generally will be made and credited to drip accounts once each week .
as of december 31 , 2018 , there were approximately 4.2 million shares available for future issuance under the drip .
anti-dilutive stock repurchase program in february 2015 , the company 2019s board of directors authorized an anti-dilutive stock repurchase program , which allowed the company to purchase up to 10 million shares of its outstanding common stock over an unrestricted period of time .
the company repurchased 0.6 million shares and 0.7 million shares of common stock in the open market at an aggregate cost of $ 45 million and $ 54 million under this program for the years ended december 31 , 2018 and 2017 , respectively .
as of december 31 , 2018 , there were 5.5 million shares of common stock available for purchase under the program. .
label: 20
qa: answer: 20
steps: op: add1-1
arg1: 12
arg2: const_4
res: 16
op: add1-2
arg1: #0
arg2: const_4
res: 20
program: add(12, const_4), add(#0, const_4)
gold_inds: text_0: intangible asset amortization expense amounted to $ 12 million , $ 4 million and $ 4 million for the years ended december 31 , 2018 , 2017 and 2016 , respectively .
exe_ans: 20
tfidftopn: text_1: estimated amortization expense for the next five years subsequent to december 31 , 2018 is as follows: .
text_7: the company repurchased 0.6 million shares and 0.7 million shares of common stock in the open market at an aggregate cost of $ 45 million and $ 54 million under this program for the years ended december 31 , 2018 and 2017 , respectively .
program_re: add(add(12, const_4), const_4)
model_input: text_0
intangible asset amortization expense amounted to $ 12 million , $ 4 million and $ 4 million for the years ended december 31 , 2018 , 2017 and 2016 , respectively .
text_1
estimated amortization expense for the next five years subsequent to december 31 , 2018 is as follows: .
text_7
the company repurchased 0.6 million shares and 0.7 million shares of common stock in the open market at an aggregate cost of $ 45 million and $ 54 million under this program for the years ended december 31 , 2018 and 2017 , respectively .