(1) In general 
Except as provided in paragraph (2), the amount of the tax imposed by subsection (a) with respect to any taxable substance shall be the amount of the tax which would have been imposed by section 4661 on the taxable chemicals used as materials in the manufacture or production of such substance if such taxable chemicals had been sold in the United States for use in the manufacture or production of such taxable substance.

(2) Rate where importer does not furnish information to Secretary 
If the importer does not furnish to the Secretary (at such time and in such manner as the Secretary shall prescribe) sufficient information to determine under paragraph (1) the amount of the tax imposed by subsection (a) on any taxable substance, the amount of the tax imposed on such taxable substance shall be 5 percent of the appraised value of such substance as of the time such substance was entered into the United States for consumption, use, or warehousing.

(3) Authority to prescribe rate in lieu of paragraph (2) rate 
The Secretary may prescribe for each taxable substance a tax which, if prescribed, shall apply in lieu of the tax specified in paragraph (2) with respect to such substance. The tax prescribed by the Secretary shall be equal to the amount of tax which would be imposed by subsection (a) with respect to the taxable substance if such substance were produced using the predominant method of production of such substance.

(1) Paragraphs (2), (5), and (9) of section 4662 (b) (relating to tax-free sales of chemicals used as fuel or in the production of fertilizer or animal feed).

(2) Paragraphs (2), (3), and (4) of section 4662 (d) (relating to refund or credit of tax on certain chemicals used as fuel or in the production of fertilizer or animal feed).