Where there has been a forgiveness of debt of the taxpayer before the end of the year that the taxpayer has disposed of all its depreciable property of a class, the undepreciated capital cost of the class at the end of the year must be determined after making the adjustments required by s. 80. S.80 will be applied where capital property of a taxpayer has been transferred to a creditor prior to the forgiveness or settlement as part of the same series of transactions.