How can customs value be determined if it can not be determined according to any of the previous valuation methods?

In the event that the customs value can not be determined in accordance with the provisions of
either the transaction value method or the method
Goods of a similar nature or method of similar goods or the method of deduction or calculation
method
In accordance with the provisions of Article VII, paragraph (2), the valuation methods used 
shall be
Article VII, is the methods developed by Articles (1 to 6) but reasonably
Flexibility in applying these methods