The value of supply of goods between the principal and his agent shall-

(a) be the open market value of the goods being supplied, or at the option of the supplier, be ninety per cent. of the price charged for the supply of goods of like kind and quality by the recipient to his customer not being a related person, where the goods are intended for further supply by the said recipient.

Illustration: A principal supplies groundnut to his agent and the agent is supplying groundnuts of like kind and quality in subsequent supplies at a price of five thousand rupees per quintal on the day of the supply. Another independent supplier is supplying groundnuts of like kind and quality to the said agent at the price of four thousand five hundred and fifty rupees per quintal. The value of the supply made by the principal shall be four thousand five hundred and fifty rupees per quintal or where he exercises the option, the value shall be 90 per cent. of five thousand rupees i.e., four thousand five hundred rupees per quintal.

(b) where the value of a supply is not determinable under clause (a), the same shall be determined by the application of rule 30 or rule 31 in that order.