1. The plaintiff's appeal and the second preliminary claim added by this court are all dismissed.

2. After an appeal is filed.

1. The reasoning of the judgment of this court citing the judgment of the court of first instance is as follows, and such reasoning is identical to the ground of the judgment of the court of first instance except for the following (the amended part).

[Revision] In the first instance judgment, the part to be modified is as follows: “The ILM type is deemed to be superior in terms of minimizing environmental pollution, upper opening, safety of driving, etc.” in the 17-18th sentence.

The details of 9 pages 15 to 17 of the judgment of the first instance shall be deleted.

2. Additional determination (as to the second preliminary claim)

A. If there is no agreement between the original defendant who is obliged to pay the Plaintiff additional service cost according to the modified design separately from the service cost according to the instant modified design service agreement, the Plaintiff’s claim against the Defendants is the primary claim of this case, premised on the existence of the above additional service cost payment agreement.

In accordance with the damages equivalent to the service cost incurred by the Plaintiff, the Defendants asserted that the amount equivalent to their respective bidding share was obligated to be returned to the Plaintiff, since they obtained unjust enrichment.

B. Article 741 of the Civil Act provides, “A person who gains a benefit from another’s property or labor without any legal cause and thereby causes loss to the other person shall return such benefit.”

In the case of the so-called unjust enrichment for which one of the parties has paid a certain amount of benefit according to his/her own will and then claims the return of the benefit on the grounds that the benefit is not a legal ground, the burden of proving that there is no legal ground

In such cases, a person who seeks the return of unjust enrichment shall, along with the existence of the fact causing the act of payment, claim and prove that the cause has ceased to exist due to the extinguishment of invalidation, cancellation, cancellation, etc., and the cause for the act of payment.