(a) No insurer shall pay commissions to an agent and no agent shall receive commissions for life insurance policies issued on a mass merchandising basis under plans sponsored by union- management employee welfare funds, which shall be in excess of the following rates for the applicable premium volume and period shown:

(b) In lieu of the above 10-year level scale, an insurer may use a scale that provides for a higher rate in the first policy year than in the next nine policy years, provided such rates are mathematically equivalent to the above scale and are approved in advance in writing by the Superintendent of Financial Services. Compensation after the tenth policy year, if payable, shall be only for the servicing of such insurance. Overriding commissions payable to a general agent shall not exceed 25 percent of commissions payable to the agent.

(c) Any increase in premiums resulting at any time from normal additions to the group of insured persons, e.g., from additions resulting from the insuring of new members, shall be treated for commission purposes as an addition to the existing premium and not as a new premium.

(d) Any increase in premiums resulting from additional insurance benefits in an insurer providing existing benefits, from a reduction in the eligibility requirements of the plan, and from the inclusion of employees of a new participating employer in the plan, may be treated for commission purposes as new premium but shall be added to the existing premium before applying the above commission scale.