In 2017, the Company’s board of directors adopted the 2017 Equity Incentive Plan (“2017 Plan”), which was approved by the Company’s stockholders. The 2017 Plan provides for the grant of incentive stock options to the Company’s employees and any parent and subsidiary corporations’ employees, and for the grant of nonstatutory stock options, stock appreciation rights, restricted stock, restricted stock units, performance units, performance shares, other cash-based awards and other stock-based awards to the Company’s employees, directors and consultants and the Company’s parent, subsidiary, and affiliate corporations’ employees and consultants. The 2017 Plan has 16,999,318 authorized shares of the Company’s Class A common stock reserved for issuance.

The following table summarizes the restricted stock units, or RSUs, awarded under the 2017 Plan for the period:

	Number of RSUs
Outstanding as of January 1, 2022		1,281,411
Granted		227,803
Vested		(323,999	)
Forfeited		(10,006	)
Outstanding as of March 31, 2022		1,175,209

The weighted average grant date fair value of the RSUs was $62.25 and the RSUs generally vest in four equal annual installments. Total compensation cost related to nonvested awards not yet recognized as of March 31, 2022, totaled $75.7 million, and is expected to be recognized over a weighted average period of 2.6 years.

The following table summarizes the stock option activity under the 2017 Plan for the period:

	Number of options			Weighted average exercise price per share		Weighted average remaining contractual term (years)		Aggregate intrinsic value (in millions)
Outstanding as of January 1, 2022		4,875,562		$	51.02		8.8
Granted		350,862		$	62.47
Exercised		(299	)	$	29.22
Forfeited		(23,355	)	$	49.37
Outstanding as of March 31, 2022		5,202,770		$	51.85		8.7	$	75.9
Exercisable as of March 31, 2022		106,826		$	47.38		7.7	$	1.8

The total intrinsic value of the 2017 Plan stock options exercised during the three months ended March 31, 2022, was not material.

The Company has an Employee Stock Purchase Plan (“ESPP”) which allows eligible employees to purchase shares of common stock through payroll deductions and is intended to qualify under Section 423 of the Internal Revenue Code. As of March 31, 2022, the Company had 3,123,191 shares of its common stock available for future issuances under the ESPP.

The purchase price for each share of common stock purchased under the ESPP will be 85% of the lower of (a) the fair market value per share on the first day of the applicable offering period or (b) the fair market value per share on the applicable purchase date.

The Company purchased 76,809 shares of common stock under the ESPP during the three months ended March 31, 2022. As of March 31, 2022, $2.4 million has been withheld on behalf of employees for a future purchase under the ESPP due to the timing of payroll deductions and is reported in Other accrued expenses and current liabilities. The Company recognized $0.7 million of stock-based compensation expense related to the ESPP for the three months ended March 31, 2022.

In connection with the acquisition of World Programming in December 2021, per the Stock Purchase Agreement, $29.5 million of the Company’s Class A Common Stock will be issued to existing employees, subject to continuing employment and certain other contingencies. The shares will be issued on the one-, two- and three-year anniversaries of the certain legal matters being resolved, subject to potential reduction in certain circumstances. The accounting treatment for these shares in the context of the business combination is to recognize the expense as a post-combination expense, not as transaction consideration.

The estimated post combination expense to the Company as a result of the World Programming business combination was approximately $29.5 million which is recognized on an accelerated method over the employment period. As of March 31, 2022, the weighted average remaining service period is 2.75 years. Once the vesting conditions of the service period are met, the Company will issue shares for each award. Stock-based compensation expense includes $4.4 million for the three months ended March 31, 2022.

In connection with the acquisition of Powersim Inc. in March 2022, per the Stock Purchase Agreement, $4.3 million of the Company’s Class A Common Stock will be issued to existing employees, subject to continuing employment and certain other contingencies. The shares will be issued on the one - and two-year anniversaries of the certain matters being resolved, subject to potential reduction in certain circumstances. The accounting treatment for these shares in the context of the business combination is to recognize the expense as a post-combination expense, not as transaction consideration. Stock-based compensation expense includes $0.2 million for the three months ended March 31, 2022.

	Three Months Ended March 31,
	2022		2021
Cost of revenue – software	$	1,903	$	1,158
Research and development		7,358		3,186
Sales and marketing		7,035		3,468
General and administrative		2,318		1,836
Total stock-based compensation expense	$	18,614	$	9,648