; and (ii) the contractor certifies that the contractor and its subcontractors have entered into a contractual agreement, or agreements, to purchase an amount of domestically melted specialty metal in the required form, for use during the period of contract performance in the production of the commercial derivative military article and the related commercial article, that is not less than the greater of— (I) an amount equivalent to 120 percent of the amount of specialty metal that is required to carry out the production of the commercial derivative military article (including the work performed under each subcontract); or (II) an amount equivalent to 50 percent of the amount of specialty metal that is purchased by the contractor and its subcontractors for use during such period in the production of the commercial derivative military article and the related commercial article. (B) Determination of amount of specialty metal required For the purposes of this paragraph, the amount of specialty metal that is required to carry out the production of the commercial derivative military article includes specialty metal contained in any item, including commercially available off-the-shelf items, incorporated into such commercial derivative military article. (10) National security waiver (A) In general Notwithstanding paragraph (1), the head of an executive agency may accept the delivery of an end item containing noncompliant materials if the head of the executive agency determines in writing that acceptance of such end item is necessary to the national security interests of the United States. (B) Requirements A written determination under subparagraph (A)— (i) shall specify the quantity of end items to which the waiver applies and the time period over which the waiver applies