418.6. The amounts to be deducted in computing cumulative Canadian oil and gas property expense of a taxpayer at any time contemplated in section 418.5 are the aggregate(a) of any amount deducted in computing his income for any taxation year ending before that time in respect of such expense;
(b) of any amount which in respect of the disposition by the taxpayer before that time of property referred to in paragraph a, c or d of section 370 or in paragraph f of section 370 in respect of property referred to in paragraph a, c or d of that section is equal to the amount by whichi. the amount by which the proceeds of disposition in respect of the property that became receivable by the taxpayer before that time exceed the aggregate of any outlays or expenses that the taxpayer made or incurred before that time for the purpose of making the disposition and that were not otherwise deductible for the purposes of this Part, exceeds
ii. the total of the amount determined under section 418.6.1 and the amount determined under section 418.6.2,
iii. (subparagraph repealed);
(c) of any amount that, before that time, becomes receivable by him and must be included in the amount contemplated in this paragraph by virtue of section 392.1;
(d) of any amount received by the taxpayer before that time in respect of a debt contemplated in paragraph c of section 418.5;
(e) of any amount of assistance that he has received or is entitled to receive in respect of any Canadian oil and gas property expense incurred after 31 December 1980 or that can reasonably be related to any such expense incurred after that date;
(e.1) of any amount by which his cumulative Canadian oil and gas property expense is required, because of section 485.8, to be reduced at or before that time; and
(f) any amount that is required to be deducted before that time under paragraph d of section 418.31 in computing his cumulative Canadian oil and gas property expense.