Equity Plans

As of May 30, 2019, 113 million shares of our common stock were available for future awards under our equity plans.

Stock Options

Stock options granted and assumptions used in the Black-Scholes option valuation model were as follows:



	Quarter ended				Nine months ended
	May 30, 2019	May 31, 2018			May 30, 2019			May 31, 2018
Stock options granted	—	—			—			2
Weighted-average grant-date fair value per share	—	$	24.14		$	19.50		$	18.61
Average expected life in years	—	5.4			5.4			5.5
Weighted-average expected volatility	—	45		%	44		%	44		%
Weighted-average risk-free interest rate	—	2.8		%	2.9		%	2.2		%
Expected dividend yield	—	0.0		%	0.0		%	0.0		%

Restricted Stock and Restricted Stock Units ("Restricted Stock Awards")

Restricted Stock Awards activity is summarized as follows:



	Quarter ended				Nine months ended
	May 30, 2019		May 31, 2018		May 30, 2019		May 31, 2018
Restricted stock award shares granted	1		—		7		4
Weighted-average grant-date fair value per share	$	40.00	$	53.77	$	39.83	$	42.14

Employee Stock Purchase Plan ("ESPP")

Our first ESPP offering period ended in January 2019 and we issued 1 million shares to employees at a purchase price per share of $32.50 under the ESPP. Assumptions used in the Black-Scholes option valuation model for the offering period beginning February 2019 were as follows:



Weighted-average grant-date fair value per share	$	10.92
Average expected life in years	0.5
Weighted-average expected volatility	47		%
Weighted-average risk-free interest rate	2.5		%
Expected dividend yield	0.0		%

Stock-based Compensation Expense



	Quarter ended				Nine months ended
	May 30, 2019		May 31, 2018		May 30, 2019		May 31, 2018
Stock-based compensation expense by caption
Cost of goods sold	$	24	$	20	$	73	$	62
Selling, general, and administrative	18		14		55		48
Research and development	16		14		48		41
	$	58	$	48	$	176	$	151

Stock-based compensation expense by type of award
Restricted stock awards	$	44	$	35	$	127	$	107
Stock options	6		13		25		44
Employee Stock Purchase Plan	8		—		24		—
	$	58	$	48	$	176	$	151

Income tax benefits related to share-based payment arrangements were $4 million and $57 million for the third quarter and first nine months of 2019, respectively, and $26 million and $142 million for the third quarter and first nine months of 2018, respectively. Income tax benefits related to share-based compensation for the first quarter of 2018 were offset by an increase in the U.S. valuation allowance. As of May 30, 2019, $385 million of total unrecognized compensation costs for unvested awards, before the effect of any future forfeitures, was expected to be recognized through the third quarter of 2023, resulting in a weighted-average period of 1.3 years.