= Solution
Far from the <diffraction> limit, and with negligible dispersion contribution, the source phase-space area scales as $\varepsilon_x\varepsilon_y$. At fixed photon flux, source-point optical functions and spectral conditions, brightness is inversely proportional to that product. The leading estimates therefore give
$$
\boxed{\frac{\mathcal B_{\rm new}}{\mathcal B_{\rm old}}\simeq8\times40=320.}
$$
Using the coupling-partition refinement in part <S19/1/b> consistently gives about $275$ instead. Both estimates assume comparable current, photon flux and insertion devices. They would cease to apply once photon <diffraction> emittance or other source-size contributions become important; the question specifically excludes that regime.
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