(a) In determining benefit rate for plan evaluation, the normal weekly earnings paid under regular employment practices will generally be used as “wages.” However, if for any extended period of time employees regularly receive extra wages, including, without limitation, overtime or premium pay, it may be required that benefits be determined on the total of normal and such extra wages.

(b) If, under a plan, benefits are to be provided in accordance with wage classifications, the maximum of each wage classification will generally be used as the weekly wage in determining the benefit rate for plan evaluation. For those employees whose average weekly wage is $20 or more and less than $40 per week, the benefit rate for plan evaluation will be computed by dividing the actual cash benefit to which the employee is entitled by $40. If the employer submits a wage schedule showing for each wage classification a distribution of employees by wages (up to weekly wages equal to twice the maximum weekly benefit payable under section 204 of the Workers' Compensation Law), the weekly wage to be used for plan evaluation will be the average wage of the employees included in the classification, but not less than $5 under the maximum wage of the classification.