(in thousands)
2019
2018
2017
Cost of revenues
$18,822
$16,862
$14,573
Selling and marketing
32,665
23,237
15,720
Research and development
18,938
15,274
13,618
General and administrative
10,484
8,489
9,402
$80,909
$63,862
$53,313
Income tax benefit
$(16,392)
$(13,383)
$(12,113)

text: 14. STOCK-BASED COMPENSATION
text: The following table presents the stock-based compensation expense included in the Company’s consolidated statements of operations:
text: The Company periodically grants stock options and restricted stock units (“RSUs”) for a fixed number of shares upon vesting to employees and non-employee Directors. Beginning in 2019, the Company granted Directors awards in the form of common stock and stock options
text: Most of the Company’s stock-based compensation arrangements vest over five years with 20% vesting after one year and the remaining 80% vesting in equal quarterly installments over the remaining four years. The Company’s stock options have a term of ten years. The Company recognizes stock-based compensation using the accelerated attribution method, treating each vesting tranche as if it were an individual grant. The amount of stock-based compensation recognized during a period is based on the value of the awards that are ultimately expected to vest. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Ultimately, the Company recognizes the actual expense over the vesting period only for the shares that vest
text: Employees may elect to receive 50% of their target incentive compensation under the Company’s Corporate Incentive Compensation Plan (the “CICP”) in the form of RSUs instead of cash. If elected by an employee, the equity amount is equal in value on the date of grant to 50% of his or her target incentive opportunity, based on the employee’s base salary. The number of RSUs granted is determined by dividing 50% of the employee’s target incentive opportunity by 85% of the closing price of its common stock on the grant date, less the present value of expected dividends during the vesting period. If elected, the award vests 100% on the CICP payout date of the following year for all participants. Vesting is conditioned upon the performance conditions of the CICP and on continued employment; if threshold funding does not occur, the RSUs will not vest. The Company considers vesting to be probable on the grant date and recognizes the associated stockbased compensation expense over the requisite service period beginning on the grant date and ending on the vesting date.
text: The Company grants awards that allow for the settlement of vested stock options and RSUs on a net share basis (“net settled awards”). With net settled awards, the employee does not surrender any cash or shares upon exercise. Rather, the Company withholds the number of shares to cover the exercise price (in the case of stock options) and the minimum statutory tax withholding obligations (in the case of stock options and RSUs) from the shares that would otherwise be issued upon exercise or settlement. The exercise of stock options and settlement of RSUs on a net share basis results in fewer shares issued by the Company.

Questions:
question: What are the company's respective stock-based compensation for  cost of revenues in 2019 and 2018?
answer: $18,822
$16,862
scale: thousand
question: What are the company's respective stock-based compensation for selling and marketing in 2019 and 2018?
answer: 32,665
23,237
scale: thousand
question: What are the company's respective stock-based compensation for research and development in 2019 and 2018?
answer: 18,938
15,274
scale: thousand
question: What is the company's average stock-based compensation for the cost of revenue between 2017 to 2019?
answer: 16752.33
derivation: ($14,573 + $16,862 + $18,822)/3 
scale: thousand
question: What is the company's average stock-based compensation for selling and marketing in 2018 and 2019?
answer: 27951
derivation: (23,237 + 32,665)/2 
scale: thousand
question: What is the company's average stock-based compensation for research and development in 2018 and 2019?
answer: 17106
derivation: (18,938 + 15,274)/2
scale: thousand