1. All of the plaintiffs' claims are dismissed.

2. The costs of lawsuit are assessed against the plaintiffs.

1. Basic facts

A. On July 15, 2008, the Defendant entered into a construction contract between the Plaintiffs and the Defendant with regard to the Section 1 (hereinafter “instant construction contract”) of the C Expansion Construction Project, on which bidding price (including value added tax), KRW 110,655,252,00, and KRW 1500, and the construction period were determined as 1,500, and the Plaintiffs participated in the instant construction project and were selected as successful bidders. 2) On November 19, 2008, the Plaintiffs entered into the construction contract with the Defendant and the instant construction project with a total construction period of KRW 1,50,943,291,00 additionally stating the total construction period as KRW 76,943,291,00 and the total construction period of the instant construction project as KRW 76,500,000 from November 20, 2008 to December 29, 2008 (hereinafter “the instant construction contract”).

3) The instant construction contract is a long-term continuing construction contract in which the total construction price is additionally stated and the annual contract is concluded within the budget of the pertinent year. Among the general conditions of the construction contract attached to the said contract (hereinafter “general conditions of the construction contract”) and the special conditions of the construction contract (Ⅰ) (hereinafter “special conditions of the construction contract”), the main contents related to the instant case are as stated in the relevant provisions. (B) The Plaintiffs and the Defendant concluded the instant construction contract with respect to the instant construction project on eight occasions from 2008 to 2015 as indicated in the following table:

(1) On December 29, 2008, the change of the total construction amount by the number of construction days from the date of completion from the date of completion of the construction work on the date of the completion of the original construction work (the additional total construction amount by the number of the vehicles during the original suspension period from November 19, 2008 to November 20, 2008, 750,000,943,291,000 on December 32, 2008 to December 32, 200,000 on December 29, 2008, the change of the total construction amount by the number of vehicles during the original suspension period from November 29, 2008 to December 31, 2008 to December 29, 2008.