((a)) ** Determination of materials; quantities** Subject to subsection (c), the President shall determine from time to time (1) which materials are strategic and critical materials for the purposes of this subchapter, and (2) the quality and quantity of each such material to be acquired for the purposes of this subchapter and the form in which each such material shall be acquired and stored. Such materials when acquired, together with the other materials described in , shall constitute and be collectively known as the National Defense Stockpile (hereinafter in this subchapter referred to as the “stockpile”).section 98c of this title
((b)) ** Guidelines for exercise of Presidential authority** The President shall make the determinations required to be made under subsection (a) on the basis of the principles stated in .section 98a(c) of this title
((c)) ** Quantity change; notification to Congress**
((1)) The quantity of any material to be stockpiled under this subchapter, as in effect on , may be changed only as provided in this subsection or as otherwise provided by law enacted after .
((2)) The President shall notify Congress in writing of any increase proposed to be made in the quantity of any material to be stockpiled that involves the acquisition of additional materials for the stockpile. The President may make the increase after the end of the 30-day period beginning on the date of the notification. The President shall include a full explanation and justification for the proposed increase with the notification.