Service portion of food supply taxed where discernible, applying to restaurants and caterers, exempting non air conditioned establishments. The document clarifies that when food or drink is supplied as part of an activity by restaurants or caterers, the value of the goods is treated as a sale and not as service, and only the residual service portion is taxable; mixed contracts may be dissected into sale and service components, and an exemption applies to establishments without air conditioning or central heating.