Solution
= Solution
The binary of <neutron stars> has $M=2.8M_\odot$ and $\mu=0.7M_\odot$. Inserting these into the circular <orbital decay timescale> gives
$$
\boxed{A_{\max}=2.38\times10^9\ \mathrm m,\qquad P_{\max}=10.5\ \mathrm h}.
$$
Using the integrated ten-billion-year merger criterion instead would give $15.2$ h.