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Contract Assets and Contract Liabilities (Details 1) - USD ($)
Dec. 31, 2020
Dec. 31, 2019
Costs and estimated earnings amounts on uncompleted contracts included in balance sheets    
Contract assets $ 1,303,136 $ 106,015
Contract liabilities (1,774,740) (168,957)
Net contract assets (liabilities) $ (471,604) $ (62,942)