= Solution
At fixed projectile <mass> and the assumed common quarter-power law, changing diameter from 30 to 75 m increases <energy> by $(75/30)^4$ and <speed> by $(75/30)^2=6.25$. The corresponding primary impact <speed> is about 15.6 km s$^{-1}$. Five percent transferred to secondary-forming ejecta gives $v_{ej}\simeq781$ m s$^{-1}$. Therefore
$$
\boxed{r_{\max}\simeq\frac{781^2}{1.622}\simeq3.76\times10^5\ \mathrm m\approx380\ \mathrm{km}.}
$$
This assumes a 45-degree launch and similar target properties/coupling, as well as the source's fixed <mass> and velocity-transfer rules. Such a range is a noticeable fraction of the lunar <radius>, so <curvature> would produce a correction; the supplied flat-surface formula is an estimate rather than exact lunar <orbit (dynamical system)>[orbit] dynamics.
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