Value of supply through agent: open market value or 90% of recipient's comparable resale price, with fallback valuation rules. Value of supply between a principal and his agent is primarily the open market value of the goods; alternatively, the supplier may opt to value the supply at ninety percent of the price charged by the recipient to its non-related customer for goods of like kind and quality when intended for further supply. If value cannot be determined under these provisions, prescribed alternative valuation methods apply in a specified sequence.