For purposes of the tax imposed by subsection (a), the value of the gross estate of every decedent to whom subsection (a) applies shall be determined as provided in section
(1) if such decedent owned (within the meaning of section
958 (a)) at the time of his death 10 percent or more of the total combined voting power of all classes of stock entitled to vote of a foreign corporation, and
(2) if such decedent owned (within the meaning of section
958 (a)), or is considered to have owned (by applying the ownership rules of section
958 (b)), at the time of his death, more than 50 percent of
(A) the total combined voting power of all classes of stock entitled to vote of such corporation, or
(B) the total value of the stock of such corporation,
then that proportion of the fair market value of the stock of such foreign corporation owned (within the meaning of section 958 (a)) by such decedent at the time of his death, which the fair market value of any assets owned by such foreign corporation and situated in the United States, at the time of his death, bears to the total fair market value of all assets owned by such foreign corporation at the time of his death, shall be included in the gross estate of such decedent. For purposes of the preceding sentence, a decedent shall be treated as owning stock of a foreign corporation at the time of his death if, at the time of a transfer, by trust or otherwise, within the meaning of sections 2035 to 2038, inclusive, he owned such stock.