2. Determination of the parties' arguments

가. 주장 원고들은, 피고가 구 임대주택법 등 관련 법령에 정해진 기준에 따라 이 사건 아파트의 정당한 분양전환가격을 산정하여야 함에도 이를 초과한 금액을 분양대금으로 원고들로부터 지급받았으므로, 피고는 원고들에게 법률상 원인 없이 취득한 분양대금 중 정당한 분양전환가격을 초과한 금액인 별지3 계산표의 ‘⑨청구금액’란 기재 각 금액 상당액을 부당이득으로 반환하여야 한다고 주장한다.

As to this, the defendant asserts that the period of extinctive prescription of the above claim is five years since the defendant's claim for return of unjust enrichment by the defendant for commercial activity following the conversion of apartment of this case into parcelling-out, and the period of extinctive prescription under Article 64 of the Commercial Act is applied. Since the plaintiffs filed the lawsuit of this case on December 5, 2013, which was five years after the conversion into parcelling-out of this case into parcelling-out, the above claim of the plaintiffs expired by extinctive prescription.

B. Article 64 of the Commercial Act may apply or apply mutatis mutandis to claims arising from judgment commercial activities as well as claims corresponding thereto (see, e.g., Supreme Court Decisions 2002Da64957 and 64964, Apr. 8, 2003; 2013Da214871, Jul. 24, 2014). The claim for return of unjust enrichment in the instant case claimed by the Plaintiffs is arising from the payment of the purchase price by the Plaintiffs based on each of the instant sales contracts concluded by the Defendant as a commercial activity, and can be deemed as arising from the sales contract that falls under commercial activities. The Defendant’s uniform calculation method was pre-sale contract with multiple lessees and lessees.