(4)Where the whole or any part of the rights is sold and the proceeds of the sale (so far as they consist of capital sums) exceed the amount of the cost of acquisition thereof remaining unallowed, so much of the excess, as does not exceed the difference between the cost of acquisition of the rights and the amount of such cost remaining unallowed shall be chargeable to income-tax as income of the business of the previous year in which the whole or any part of the rights is sold.Explanation. - Where the whole or any part of the rights is sold in a previous year in which the business is no longer in existence, the provisions of this sub-section shall apply as if the business is in existence in that previous year.
