Section 25. The apportionment of the total revenues accruing from the sale of lottery tickets or shares and from all other sources shall be as follows:—(a) the payment of prizes to the holders of winning tickets or shares which in any case shall be no less than forty-five per cent of the total revenues accruing from the sale of lottery tickets; (b) the payment of costs incurred in the operation and administration of the lottery, including the expenses of the commission and the costs resulting from any contract or contracts entered into for promotional, advertising or operational services or for the purchase or lease of lottery equipment and materials which in no case shall exceed fifteen per cent of the total revenues accruing from the sale of lottery tickets, subject to appropriation; and (c) the balance to be used for the purposes set forth in clause (c) of section thirty-five.