pre_text: The following table illustrates the classification of pre-payroll tax and social contribution stock-based compensation expense included in the consolidated statements of income for the years ended December 31, 2019, December 31, 2018 and December 31, 2017: The fair value of the shares vested in 2019 was $114 million compared to $68 million for 2018 and $38 million for 2017. Compensation cost, excluding payroll tax and social contribution, capitalized as part of inventory was $6 million as of December 31, 2019, compared to $6 million as of December 31, 2018 and $3 million as of December 31, 2017. As of December 31, 2019, there was $138 million of total unrecognized compensation cost related to the grant of unvested shares, which is expected to be recognized over a weighted average period of approximately 9 months. The total deferred income tax benefit recognized in the consolidated statements of income related to unvested share-based compensation expense amounted to $9 million, $7 million and $3 million for the years ended December 31, 2019, 2018 and 2017, respectively.
table: December 31, 2019 December 31, 2018 December 31, 2017
table: Cost of sales 22 23 12
table: Selling, general and administrative 46 67 31
table: Research and development 77 35 18
table: Total pre-payroll tax and social contribution compensation 145 125 61
question: Analyse this data from a financial earnings document. What was the average of Selling, general and administrative?