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Intangible Assets, Net (Tables)
9 Months Ended
Sep. 30, 2020
Intangible Assets, Net [Abstract]  
Schedule of intangible assets
   December 31,   September 30, 
   2019   2020 
Computer software at cost  $30,648   $31,429 
Accumulated amortization   (15,470)   (19,422)
   $15,178   $12,007