3Entertainments duty on season tickets, and c.
Where—
(a)the payment for admission to an entertainment is made by means of a lump sum paid as a subscription or contribution to any club, association or society, or for a season ticket or for the right of admission to a' series of entertainments or to any entertainment during a certain period of time ; and
(b)the person making the payment could have obtained the same rights of admission to entertainments (being entertainments in respect of which entertainments duty is payable) by making separate payments of ascertained amounts in respect of all those entertainments,
the duty chargeable in respect of the lump sum payment shall not exceed the total sums which would have been payable by way of entertainments duty if, in lieu of making the lump sum payment, he had made those separate payments.