held that a company`s negative net assets should not be ignored or not taken into account when determining capital gains in a slump sale and that the same cannot be equated to zero and that the same should be added to the counter-performance of the sale to obtain the capital gains. Slump Sale means in principle the transfer of one or more companies as a result of the sale for a lump sum consideration, without any value being attributed to each asset and liability. . . .