21.20.1R1. For the purposes of paragraph d of section 21.20.1 of the Act, the prescribed rate of interest in effect during a particular period is equal(a) where the shares referred to in that paragraph d were issued before 1 January 1984, to the rate determined in respect of that period for the purposes of subsection 1 of section 161 of the Income Tax Act (R.S.C. 1985, c. 1 (5th Suppl.)); and
(b) where the shares referred to in that paragraph d were issued after 31 December 1983, to the rate determined in respect of that period in accordance with subparagraph i of paragraph a of section 4301 of the Income Tax Regulations made under the Income Tax Act.