Annually, in the month of April, the commissioner may review the rates of every health service corporation, and shall, not later than 60 days after April 1 of each year, provided that the corporation has filed all pertinent data, make adjustments thereto, if any, as are just and reasonable. Whenever the contingency reserve fund of a health service corporation shall be less than 8 percent of its annual premium income, the commissioner shall permit the corporation to charge rates designed to enable it to increase its contingency reserve fund by an amount equal to at least 2 percent of the annual premium income of the corporation. If the liabilities of a health service corporation exceed its assets, however, the commissioner shall permit the corporation to charge rates designed to enable the corporation to accumulate such a reserve fund by an amount equal to at least 5 percent of the annual premium income of the corporation until such time as the assets of the corporation equal its liabilities. In no event shall the commissioner permit a health service corporation to charge rates which would result in a reserve fund in excess of 20 percent of the annual premium volume of the corporation. This section shall not preclude the granting of appropriate rate changes at any other times. In connection with a rate decision, the commissioner may also make reasonable supplemental orders to the health service corporation and may attach reasonable conditions and limitations to such orders as the commissioner finds, on the basis of competent and substantial evidence, necessary to insure that benefits and services are provided at minimum cost under efficient and economical management of the corporation.