 Solution

The printed aerial image has approximately $I_{\max }=2.0$ and $I_{\min }=0.5\mathrm{mW}\mathrm{c}{\mathrm{m}}^{-2}$. Thus its modulation, and its modulation transfer for a fully modulated object, isThe image does not meet the full-thickness printing criterion, because $0.60<0.667$. Equivalently, clearing the bright regions requires $t\ge 100/2=50$ s, while preserving the full thickness in the dark regions requires $t\le 20/0.5=40$ s. There is no common exposure time.

Partial thickness modulation may remain visible, but that is different from a clean grating with fully cleared spaces and retained full-thickness lines. Small ripple peaks in the source drawing do not change this conclusion.