(a) When all of the employee's employment during the eight weeks immediately preceding and including his last day worked prior to commencement of disability has been performed in the employ of a single covered employer, the average weekly wage shall be the amount determined either by dividing the total wages paid such employee by such employer during the last eight weeks immediately preceding and including his last day worked prior to commencement of such disability; or on the same basis, but excluding the week in which the disability began (whichever is the higher amount) by the number of weeks during which he worked on at least one day during such eight- or seven-week period.

(b) When the employee is in the employment of more than one covered employer at the commencement of disability, the average weekly wage with respect to employment with each such employer shall be the amount determined either by dividing the total wages paid the employee by such employer during the last eight weeks immediately preceding and including his last day worked prior to commencement of such disability; or on the same basis, but excluding the week in which the disability began (whichever is the higher amount) by the number of weeks during which he worked on at least one day during such eight- or seven-week period with such employer.

(c) When all of the employee's employment during the eight weeks immediately preceding and either including his last day worked prior to commencement of such disability, or excluding the week in which the disability began, has not been performed in the employ of his last covered employer (or employers if concurrently eligible for benefits to be provided by more than one covered employer), the average weekly wage shall be determined either by dividing the total wages received from his last covered employer (or employers if concurrently eligible for benefits from more than one covered employer) during the last eight weeks immediately preceding and including his last day worked prior to commencement of such disability, or on the same basis, but excluding the week in which the disability began (whichever is the higher amount) by the number of weeks during which he worked on at least one day during such eight- or seven-week period, in such employment(s).

(d) In the event the computation of average weekly wage is made pursuant to subdivision (b) or (c) of this section and the employee notifies the employer or the carrier that the average weekly wage upon which his benefits were computed does not fairly represent his normal earnings and the employee presents a statement reasonably identifying his former covered employers and the amount of wages received from such employers to support this contention, the average weekly wage will again be computed by dividing the total wages received from all covered employers during the eight weeks immediately preceding and including his last day worked prior to commencement of such disability by the number of weeks during which he worked on at least one day in such employment. The higher average weekly wage arrived at by this method or the method provided under subdivision (b) or (c) of this section, whichever is applicable, shall be used as the employee's average weekly wage.

(e) The average weekly wage to be used under any plan may be computed in accordance with the provisions of such plan filed with and accepted by the chairman.

(f) An employer may, in accordance with regular practice, compute average weekly wage on the basis of payroll weeks; provided, however, that any employee of such employer may request that the period used include the last day worked.