(a) Each corporation affected by this Part shall keep such records of property and property retirements as will reflect, so far as practicable, the service life of all property retired, and will permit the determination of the age of all existing property; and also such records as will reflect the salvage and cost of removal of property retired from each account including property used wholly or partly in steam operations.

(b) Each such corporation shall also maintain such records supporting its books of account as are necessary to show the reserves accumulated to provide for depreciation or ultimate retirement of its property used wholly or partly in steam operations, separately for each operating property or fixed capital account.