of the maximum amount described in section 2(c), the head of each department or agency listed in section 3(b) shall remit to the general fund of the Treasury an amount, to be derived from the unobligated balances of each appropriate account of such department or agency, that is equal to the extent to which the head of such department or agency determines that such balance remains unobligated because of the expenditures by the Secretary of Homeland Security, pursuant to the appropriation under section 2(a), to secure the international border between the United States and Mexico. (b) Annual report Not later than November 1 of the first fiscal year beginning after the date of the enactment of this Act, and annually thereafter, the head of each department or agency listed in section 3(b) shall jointly submit to Congress a report including any amount saved by each such department or agency on expenditures relating to aliens unlawfully present in the United States in the preceding fiscal year because of the expenditures of the Secretary of Homeland Security, pursuant to the appropriation under section 2(a), to secure the international border between the United States and Mexico.