Where, subsequent to the exercise of the option provided for in the first paragraph of II of article 208 C, real estate, rights in rem mentioned in the sixth paragraph of II of the same article, rights relating to a leasing contract on real estate, rights relating to real estate the enjoyment of which has been granted on a temporary basis by the State, a local authority or one of their public establishments or shareholdings in persons referred to in Article 8 become eligible for the exemption mentioned in this paragraph, the company must add back to its taxable income subject to corporation tax a sum corresponding to the capital gain calculated as the difference between the actual value of these assets on that date and their tax value. This reintegration is made in equal parts over a period of four years. The disposal of the assets in question results in immediate taxation of the capital gain that has not yet been added back.