The interest rates for motor vehicle financing shall be that authorized by subdivision 41a(b)(4) of this title, and the method of interest calculation shall be as specified in subsection 41a(d) of this title. (Added 1979, No. 173 (Adj. Sess.), § 15, eff. April 30, 1980; amended 1989, No. 122, § 7, eff. June 30, 1989.)