Solution
= Solution
Write $\epsilon=1-q$ and $b/a=1-s$. Then $\log(1-s)=-s+O(s^2)$ and $\log q=-\epsilon+O(\epsilon^2)$, giving
$$
\boxed{L_c\simeq\frac{s}{1-q}.}
$$
The largest permitted integer is still selected by the strict inequality from part (b). This says that longer master sequences need a proportionately larger selective advantage or smaller per-digit copying error.