44. For the purposes of this chapter, investment interest in a business at the end of a taxation year means, for a taxpayer that is a corporation, the lesser of:(a) the aggregate that would be determined under section 43 if it were to apply to a corporation; and
(b) its 1971 accounts receivable, decreased at the rate of 10% per annum computed on the straight-line method for each taxation year ending after 1971 and either before or at the same time as the taxation year.