Where in the case of any goods tax is leviable at one point in a series of sales or purchases, such series shall, -

(a) in the case of goods imported into the State either from outside the territory of India or from any other State in India, be deemed to commence at the stage of the sale or purchase effected immediately after the import of such goods;

(b) in the case of goods exported out of the State to any place outside the territory of India or to any other State in India, be deemed to conclude at the stage of the sale or purchase effected immediately before the export of such goods.-