99.20. Not later than 1 April 1989, the Commission shall cause to be prepared by the actuaries it designates the valuation of the actuarial value of the benefits provided for in section 99.19 and of the sums intended for their funding. The premium paid or payable by the employer in relation, as the case may be, to persons who have availed themselves of any of the measures provided in subdivision 3 and who continue to be covered by the basic health insurance plan in accordance with the conditions of employment applicable to them must be added to the actuarial value of such benefits.