80. For the purpose of computing, at any particular time after 1971, the adjusted cost base to a taxpayer of an interest in a partnership of which he was a member on 31 December 1971 and thereafter without interruption until that time, section 257 of the Taxation Act (chapter I-3) is deemed to require the deduction of the lesser of:(a) the amount by which all amounts determined under paragraph a of section 78 exceed the aggregate of the amounts determined under paragraphs a and b of section 77, and
(b) the amount by which all the amounts determined as of that time in respect of that interest under section 83 exceed the aggregate of those determined under section 82.