For the purpose of paragraph 3(c), price undercutting shall include any case in which such price undercutting has been demonstrated through a comparison of prices of the subsidized product with prices of a non-subsidized like product supplied to the same market. The comparison shall be made at the same level of trade and at comparable times, due account being taken of any other factor affecting price comparability. However, if such a direct comparison is not possible, the existence of price undercutting may be demonstrated on the basis of export unit values.