Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
열발생은 에너지 효율성을 높이는 데 중요합니다.yeolbalsaengeun eneoji hyoyulseong-eul nopineun de jungyohamnida.Heat generation is important for improving energy efficiency.