STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2021

The following table summarizes the components of stock-based compensation expense included in the consolidated statements of operations:

	Three Months Ended March 31,
	2021		2020
Stock-Based Compensation Expense:
Cost of revenue	$	71	$	45
Sales and marketing expense		505		94
Research and development expense		229		187
General and administrative expense		405		363
	$	1,210	$	689

	Three Months Ended March 31,
	2021		2020
Stock-based compensation expense by type:
Employee stock purchase plan	$	1,085	$	431
Non-employee stock purchase plan		40		172
Subsidiary option grants		85		86
	$	1,210	$	689

The fair value of options granted to employee with a service period based condition is estimated on the grant date using the Black-Scholes valuation.

(1)	Equal to closing value on the grant date.

(2)	Expected term of share options is based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110.

(3)	Volatility is calculated based on the historical volatility of ACM’s comparable companies in the period equal to the expected term of each grant.

(4)	Risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant.

(5)	Expected dividend is assumed to be 0% as ACM has no history or expectation of paying a dividend on its common stock.

The following table summarizes the Company’s employee share option activities during the three-months ended March 31, 2021:

	Number of Option Share	Weighted Average Grant Date Fair Value		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term
Outstanding at December 31, 2020	3,191,411	$	5.13	$	12.73	7.13 years
Granted	106,400		50.67		111.98
Exercised	(255,582)		1.78		4.55
Forfeited/cancelled	(11,989)		27.45		62.58
Outstanding at March 31, 2021	3,030,240		6.93	$	16.70	7.22 years
Vested and exercisable at March 31, 2021	1,809,322

The following table summarizes the ACM Shanghai employee stock option activities during the three months ended March 31, 2021:

	Number of Option Shares in ACM Shanghai	Weighted Average Grant Date Fair Value		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term
Outstanding at December 31, 2020	5,423,654	$	0.23	$	1.89	3.50 years
Granted	-		-		-
Exercised	-		-		-
Expired	-		-		-
Forfeited/cancelled	(46,154)		0.24		2.00
Outstanding at March 31, 2021	5,377,500	$	0.24	$	2.00	3.26 years
Vested and exercisable at March 31, 2021	-

The following table summarizes the Company’s non-employee share option activities during the three months ended March 31, 2021:

	Number of Option Shares	Weighted Average Grant Date Fair Value		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term
Outstanding at December 31, 2020	836,038	$	1.02	$	3.07	4.92 years
Granted	-		-		-
Exercised	(54,358)		1.51		5.44
Expired	-		-		-
Forfeited/cancelled	(76)		0.30		0.75
Outstanding at March 31, 2021	781,604	$	0.99	$	2.91	4.64 years
Vested and exercisable at March 31, 2021	773,139