If a manufacturer that imports or purchases compressors from another manufacturer for making air handling units of central air conditioning systems follows the provisions stipulated in Article 75 of the Regulations for the Collection of Commodity Tax instead of the provisions above in tax reporting, it should apply to the tax authority for computation of commodity tax pursuant to Article 3 herein. Notwithstanding the foregoing, a manufacturer may not adopt more than one method of tax computation, and may not apply for change of method within three years after a method has been approved.