1. The Defendant shall pay KRW 19,650,00 to the Plaintiff the annual rate of KRW 15% from April 8, 2016 to the date of complete payment.

1. Basic facts

A. On June 2015, the Plaintiff consulted on the construction work with the content of manufacturing and installing a water tank at a bath designated by the Defendant.

B. On June 6, 2015, the Plaintiff presented the first written estimate to the Defendant “STS316, 13,500,000 won for a hot water tank (STS316), 1st 1,800,000 won for a hot water tank (STS), and 1st 1st 2,600,000 won for a sealed-type inflation tank (excluding value-added tax).”

The Defendant requested the Plaintiff to change the value of the first quotation to another water-supply tank (STS316) higher than the “oil tank (STS316)”.

Accordingly, on July 9, 2015, the Plaintiff presented a second written estimate to the Defendant “STS304, 11,800,000 won for hot water tank (STS304), 1,800,000 won for hot water tank (S400), and 16,200,000 won for sealed-type inflation tank (S40) for total of 16,20,000 won for value added tax (excluding value added tax).”

C. On July 14, 2015, the Plaintiff and the Defendant consulted on the construction cost based on the second estimate, and entered into a contract for supply and installation of the oil tank (STS304) (hereinafter “instant construction”) with the Plaintiff as the construction cost of KRW 15,950,00 (including value added tax) for the bath bath designated by the Defendant.

On July 22, 2015, Yusung Construction Co., Ltd. jointly and severally guaranteed the Defendant’s obligation to pay the construction cost to the Plaintiff according to the instant contract.

E. The Plaintiff manufactured and completed a water tank (STS304) pursuant to the instant contract.

However, the defendant requested to change the existing water-supply tank (STS304) to other water-supply tank (STS316).

Accordingly, the plaintiff and the defendant decided to change and install a water-supply tank (STS304) installed in the past to a different water-supply tank (STS316) and to increase the construction cost by adding the construction cost to 7,700,000 won (including value-added tax).

F. On August 31, 2015, the Plaintiff changed the water-supply tank (STS304) installed in the past to another water-supply tank (STS316) and completed the manufacture and installation of the water-supply tank.

G. The Plaintiff on January 2016.