This section shall apply to a new holding—
Where for the purpose of computing the gain or loss accruing to a person from the acquisition and disposal of the whole or any part of any class of shares or debentures or rights of unit holders forming part of a new holding to which this section applies it is necessary to apportion costs of acquisition between what is disposed of and what is retained, the cost of acquisition of the new holding shall first be apportioned between the entire classes of shares or debentures or rights of which it consists by reference to market value on the first day (whether that day fell before the reorganisation took effect or later) on which market values or prices were quoted or published for the shares, debentures or rights as mentioned in subsection (1)(a) or (1)(b) above (with such adjustment of the market value of any class as may be required to offset any liability attaching thereto but forming part of the cost to be apportioned).
For the purposes of this section the day on which a reorganisation involving the allotment of shares or debentures or unit holders' rights takes effect is the day following the day on which the right to renounce any allotment expires.