Gravitation

Two satellites \(A\) and \(B\) revolve round the same planet in coplanar circular orbits lying in the same plane. Their periods of revolutions are \(1 \mathrm{~h}\) and \(8 \mathrm{~h}\), respectively. The radius of the orbit of \(A\) is \(10^4 \mathrm{~km}\). The speed of \(B\) is relative to \(A\). When they are closed in \(\mathrm{km} / \mathrm{h}\) is