If the Sales Tax Officer finds no difficulty in ascertaining whether the goods are delivered in a State only for the purpose of consumption within that State or whether they were delivered for the purpose of resale out of that State so as to ascertain the applicability of the Explanation to clause (1) (a), why cannot the same officer find out what goods were purchased by the exporters for the purpose of export or what part of the imported goods were sold by the importers to the dealers ? If the Income tax Officer can without difficulty ascertain the income, profits and gains of a business and work out the provisions of, section 10 of the Indian Income tax Act and also can ascertain under section 42 of that Act the income deemed to accrue or arise within the taxable territory, there cannot be any insuperable difficulty in the way of the Sales Tax Officer determining the turnover of a particular dealer and working out the exemptions he is entitled to under article 286(1) (b).