For the purposes of this Act, a reference to assessable exploration recovery receipts derived by a person in relation to a petroleum project is a reference to:
(a) where any petroleum, or a constituent of petroleum, recovered from the eligible exploration or recovery area (other than any production licence area) in relation to the project is or was sold, whether processed or unprocessed, before any marketable petroleum commodity is or was produced from it--the consideration receivable, less any expenses payable, by the person in relation to the sale;
(b) where any marketable petroleum commodity produced from petroleum recovered from the area to which paragraph (a) applies becomes or became an excluded commodity by virtue of being sold--the consideration receivable, less any expenses payable, by the person in relation to the sale; and
(c) where any marketable petroleum commodity produced from petroleum recovered from the area to which paragraph (a) applies becomes or became an excluded commodity otherwise than by virtue of being:
(i) sold; or
(ii) treated or processed, or moved, for re - injection or destruction or for use in carrying on or providing operations, facilities or other things of a kind referred to in section 37, 38 or 39 in relation to the petroleum project;
so much of the market value of the commodity immediately before it becomes or became an excluded commodity, or, where there is insufficient evidence of that market value, of such amount as, in the opinion of the Commissioner, is fair and reasonable, as is taken by section 26 to be derived by the person.