(1) Each progressive or periodic supply shall be treated as separate supply.

(2) If each of the progressive or periodic supplies is not readily separable, such supply shall be treated as a series of separate supplies, each corresponding to the proportion of the supply to which such separate part of the consideration relates.

(3) In relation to each part of a supply under a lease or of a right to use any property, the time required continuously over the period of such lease or right of use shall be treated as the time of supply.