20.1. Where section 33 of the Act respecting the Pension Plan of Management Personnel (chapter R-12.1) applies, the service established in accordance with sections 19 and 20 of this Act shall be credited with up to one year in excess of the service credited under the Pension Plan of Management Personnel. The pensionable salary attached to pensionable employment under this plan shall be determined in accordance with Division I of this chapter, multiplied by the service credited pursuant to the first paragraph over the service established in accordance with sections 19 and 20 of this Act.