For the purposes of subsection (2) of section 69 of the Act, where five percent or more of the underlying ownership of an entity that holds petroleum rights in the country is disposed off, to determine the gain from the disposal,

(a) the written down value of the capital allowance expenditure of the entity at the beginning of the year in which its underlying ownership was disposed off shall, be apportioned in proportion to the percentage of the underlying ownership disposed off; and

(b) deduct from the consideration derived from the disposal or from the market value of the proportion of the right deemed to be disposed off, whichever is higher.