“base cost” means the base cost as defined in paragraph 1 of the Eighth Schedule: Provided that where the base cost of an asset as at a specific date is to be determined as contemplated in paragraph 26 or 27 of the Eighth Schedule, the amount thereof must, for purposes of section 42 or 44, be determined as if that asset had been disposed of on that date for an amount received or accrued equal to the market value of that asset as at that date;