For the purposes of subsection (a)(5)(B) of this section, the term “cash flow financing” means the dollar amount of the difference between the total estimated price of a Letter of Offer and Acceptance or other purchase agreement that has been approved for financing under this chapter or under section 503(a)(3) of the Foreign Assistance Act of 1961 [
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(a)(3)] and the amount of the financing that has been approved therefor;