pre_text: Note 11: Share-Based Compensation Total share-based compensation expense related to the Company's stock options, RSUs, stock grant awards and ESPP were recorded within the Consolidated Statements of Operations and Comprehensive Income as follows (in millions): (1) Recognition of related income tax benefits are the result of the adoption of ASU 2016-09 during the first quarter of 2017 through a cumulative effect adjustment of $68.1 million recorded as a credit to retained earnings as of January 1, 2017. Tax benefit is calculated using the federal statutory rate of 21% during the years ended December 31, 2019 and December 31, 2018, and 35% for the year ended December 31, 2017. At December 31, 2019, total unrecognized share-based compensation expense, net of estimated forfeitures, related to non-vested RSUs with service, performance and market conditions was $74.9 million, which is expected to be recognized over a weighted-average period of 1.3 years. The total intrinsic value of stock options exercised during the year ended December 31, 2019 was $3.9 million. The Company received cash of $1.7 million and $26.2 million from the exercise of stock options and the issuance of shares under the ESPP, respectively. Upon option exercise, vesting of RSUs, stock grant awards, or completion of a purchase under the ESPP, the Company issues new shares of common stock.
table: Year Ended December 31,
table: 2019 2018 2017
table: Cost of revenue $10.6 $7.0 $6.0
table: Research and development 17.0 14.3 12.5
table: Selling and marketing 14.8 14.1 11.7
table: General and administrative 37.0 42.9 39.6
table: Share-based compensation expense 79.4 78.3 69.8
table: Related income tax benefits at federal rate (1) (16.7) (16.4) (24.4)
table: Share-based compensation expense, net of taxes $62.7 $61.9 $45.4
question: Analyse this data from a financial earnings document. What is the change in Cost of revenue from December 31, 2018 to 2019?