...The amounts appropriated by clauses (3) and (4) of this subsection shall be transferred from time to time from the general fund in the Treasury to the Federal Old-Age and Survivors Insurance Trust Fund, and the amounts appropriated by clauses (1) and (2) of subsection (b) of this section shall be transferred from time to time from the general fund in the Treasury to the Federal Disability Insurance Trust Fund, such amounts to be determined on the basis of estimates by the Secretary of the Treasury of the taxes, specified in clauses (3) and (4) of this subsection, paid to or deposited into the Treasury; and proper adjustments shall be made in amounts subsequently transferred to the extent prior estimates were in excess of or were less than the taxes specified in such clauses (3) and (4) of this subsection. All amounts transferred to either Trust Fund under the preceding sentence shall be invested by the Managing Trustee in the same manner and to the same extent as the other assets of such Trust Fund...