3. Manner of determination of value.
Subject to the provisions of section 67, the value of taxable service, where such value is not ascertainable, shall be determined by the service provider in the following manner :-
(a) the value of such taxable service shall be equivalent to the gross amount charged by the service provider to provide similar service to any other person in the ordinary course of trade and the gross amount charged is the sole consideration;
(b) where the value cannot be determined in accordance with clause (a), the service provider shall determine the equivalent money value of such consideration which shall, in no case be less than the cost of provision of such taxable service.