not to exceed, for such part of the project as may be attributable to dwelling use (excluding exterior land improvements as defined by the Secretary), $42,048 per family unit without a bedroom, $48,481 per family unit with one bedroom, $58,469 per family unit with two bedrooms, $74,840 per family unit with three bedrooms, and $83,375 per family unit with four or more bedrooms; except that as to projects to consist of elevator-type structures the Secretary may, in his discretion, increase the dollar amount limitations per family unit to not to exceed $44,250 per family unit without a bedroom, $50,724 per family unit with one bedroom, $61,680 per family unit with two bedrooms, $79,793 per family unit with three bedrooms, and $87,588 per family unit with four or more bedrooms, as the case may be, to compensate for the higher costs incident to the construction of elevator-type structures of sound standards of construction and design; (B) the Secretary may, by regulation, increase any of the dollar limitations in subparagraph (A) (as such limitations may have been adjusted in accordance with section 1712a of this title) by not to exceed 170 percent in any geographical area where the Secretary finds that cost levels so require and by not to exceed 170 percent, or 215 percent in high cost areas, where the Secretary determines it necessary on a project-by-project basis, but in no case may any such increase exceed 90 percent where the Secretary determines that a mortgage purchased or to be purchased by the Government National Mortgage Association in implementing its special assistance functions under section 1720 1 of this title (as such section existed immediately before November 30, 1983) is involved; and