(b) Installment payments and deferral. In the event that any portion of the federal transfer tax is deferred or to be paid in installments under the provisions of the Internal Revenue Code, the portion of the Illinois transfer tax which is subject to deferral or payable in installments shall be determined by multiplying the Illinois transfer tax by a fraction, the numerator of which is the gross value of the assets included in the transferred property having a tax situs in this State and which give rise to the deferred or installment payment under the Internal Revenue Code, and the denominator of which is the gross value of all assets included in the transferred property having a tax situs in this State. Deferred payments and installment payments, with interest, shall be paid at the same time and in the same manner as payments of the federal transfer tax are required to be made under the applicable Sections of the Internal Revenue Code, provided that the rate of interest on unpaid amounts of Illinois transfer tax shall be determined under this Act. Acceleration of payment under this Section shall occur under the same circumstances and in the same manner as provided in the Internal Revenue Code.