For the purposes of this formula,(1) A is the particular amount referred to in subparagraph 2 of the first paragraph of section 457.1.4;
(2) B is the amount determined under the second paragraph of section 457.1.4;
(3) C is the composite amount referred to in subparagraph 1 of the first paragraph of section 457.1.4; and
(4) D is the amount of the input tax refund claimed by the registrant, in a fiscal year, in relation to the composite amount.