| 
 Costs,
estimated earnings and billings on uncompleted contracts are as follows: 
  
    |   | 
      | 
    June 30, | 
      | 
    December 31, | 
 
    |   | 
      | 
    2015 | 
      | 
    2014 | 
 
    |   | 
      | 
      | 
      | 
      | 
 
    | Revenue
    Recognized | 
      | 
    $ | 
    384,500 | 
      | 
      | 
    $ | 
    168,700 | 
      | 
 
    | Less:
    Billings to date | 
      | 
      | 
    (199,100 | 
    ) | 
      | 
      | 
    (107,600 | 
    ) | 
 
    | Costs
    and estimated earnings in excess of billings on uncompleted contracts | 
      | 
    $ | 
    185,400 | 
      | 
      | 
    $ | 
    61,100 | 
      | 
 
    |   | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
      | 
 
    | Billings
    to date | 
      | 
    $ | 
    3,790,800 | 
      | 
      | 
    $ | 
    1,250,900 | 
      | 
 
    | Revenue
    recognized | 
      | 
      | 
    (3,324,400 | 
    ) | 
      | 
      | 
    (942,400 | 
    ) | 
 
    | Billings
    in excess of costs and estimated earnings on uncompleted contracts | 
      | 
    $ | 
    466,400 | 
      | 
      | 
    $ | 
    308,500 | 
      | 
 
 
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