(a) Each handler who first handles potatoes shall, with respect to the potatoes so handled by him, pay to the committee such handler's pro rata share of the expenses which the Secretary finds will be necessarily incurred by the committee for its maintenance and functioning during each fiscal year. Such handler's pro rata share of such expenses shall be equal to the ratio between the total quantity of potatoes handled by him as the first handler thereof, during the applicable fiscal year, and the total quantity of potatoes handled by all handlers as the first handlers thereof, during the same fiscal year. The Secretary shall fix the rate of assessment to be paid by such handlers: Provided, That the rate of assessment during each fiscal year shall not exceed 1 cent per hundred-weight.
(b) At any time during or after a fiscal year, the Secretary may increase the rate of assessment in order to secure sufficient funds to cover any later finding by the Secretary relative to the expenses of the committee. Such increase shall be applicable to all potatoes handled during the given fiscal year. In order to provide funds to carry out the functions of the committee, handlers may make advance payment of assessments.