= Solution
The slit transmissions have the same magnitude but opposite phase. An ideal narrow-slit representation is
$$
\boxed{T(y)\propto\delta(y+d/2)-\delta(y-d/2),\qquad d=0.1\,\mathrm{mm}.}
$$
Equivalently draw two narrow rectangles at $y=\pm d/2$, one at+1 and the other at−1, and zero elsewhere. A finite rectangle width gives each slit its own diffraction envelope. The original aperture plot shows such rectangles with explicitly illustrative width; the negative value is a field phase reversal, not negative transmitted intensity.
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