4. Determination of value of supply by comparison
(1) Where the value of a supply cannot be determined under rule 3, the value shall be determined on the basis of the transaction value of goods and/or services of like kind and quality supplied at or about the same time to other customers, adjusted in accordance with the provisions of sub-rule (2).
(2) In determining the value of goods and/or services under sub-rule (1), the proper officer shall make such adjustments as appear to him reasonable, taking into consideration the relevant factors, including-
(a) difference in the dates of supply,
(b) difference in commercial levels and quantity levels,
(c) difference in composition, quality and design between the goods and/or services being valued and the goods and/or services with which they are compared,
(d) difference in freight and insurance charges depending on the place of supply.
