1. The court's explanation on this part of the basic facts is the same as the corresponding part of the judgment of the court of first instance, and thus, citing it by the main text of Article 420 of the Civil Procedure Act.

2. Determination as to the claim on the principal lawsuit

A. 1) The Plaintiff’s assertion as to the instant construction works is that the subcontract concluded between the Plaintiff and the Defendant regarding the instant construction works is a unit price contract. As such, the Defendant is obligated to pay the increased construction cost with respect to the instant construction works, the quantity of which exceeds the quantity specified in the contract, and the Plaintiff’s claim as a principal lawsuit.

B) As to the construction cost, until April 30, 209, the progress rate of the instant mechanical pipeline construction by the Plaintiff at the site is 50.04%, and 56.57%, the Defendant is obligated to pay the additional construction cost of USD 1,94,556 ($3,890,000 in contract amount x 50.04% in total), USD 3,111,399 in total as to the completion payment for the boiler construction of this case ($ 5,500 in contract amount x 56.57% in total) from USD 5,057,955 in total, and USD 2,00 in total from USD 36,00 in the form of the boiler construction of this case, USD 2,00 in total, KRW 756,70 in total, and KRW 186 in total from USD 86 in the form of the raw material of the instant boiler construction, and the Defendant is obligated to pay the Plaintiff’s additional construction cost of 186,7.75.75.