the Service of accomplishing the work of the full sets of furnished air-conditioning of water-cooled system to the said Premised to which the Owner shall be solely responsible for full installation of cool conduits and condensing unit including all of major repairing caused by normal and ordinary usage and minor maintenance and air-conditioning water-cooled expenses all of which shall be paid by the Owner so the Owner shall not collect any charges during the said agreed fixed period of the normal ordinary working hours But the Tenant shall have to make payments for extra time at the rate of Baht 300 per one hour when using before or after the agreed fixed period of the normal ordinary working hours.