4.11 About half the less accessible civil infrastructure assets, known as grey assets, had not been classified at the date of contract and are required to be classified within the first review period. This material un-priced contract scope compounds the difficulty of knowing whether the contract closing position represents an economic & efficient proposition and agreeing these further costs will provide a test for the contract structure and the Arbiter. By design, if asked to by any of the parties to the contract, the Arbiter is given the final word in judging, based on good industry practice, what would be economic and efficient for dealing with assets in each particular classification and set of circumstances.