Annual report pursuant to Section 13 and 15(d)

8. STOCKHOLDERS' EQUITY (Details)

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8. STOCKHOLDERS' EQUITY (Details)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dividend yield 0.00% 0.00%
Minimum    
Expected term 5 years 9 months 18 days 5 years 9 months 18 days
Volatility 54.00% 54.00%
Risk-free interest rate 1.36% 2.40%
Maximum    
Expected term 6 years 3 months 18 days 6 years 3 months 18 days
Volatility 63.00% 57.00%
Risk-free interest rate 2.92% 3.11%