To carry out the provisions of this subchapter, there are authorized to be appropriated—

(1) for the fiscal year ending June 30, 1976, $75,000,000;

(2) for subsequent fiscal years, only such sums as the Congress hereafter may authorize by law;

(3) such amounts as may be authorized for the construction of demonstrations pursuant to section 5556(f) of this title; and

(4) to the National Science Foundation for the fiscal year ending June 30, 1975, not to exceed $2,000,000 to be made available for use in the preparation of the comprehensive program definition under section 5564 of this title.