Gravitation

Two spherical bodies A and B each of mass $M$ and radius $R$ are located such that their centers are apart by a distance of $4 R$ as shown in the figure. An object $C$ of mass $m$ is thrown from the surface of A directly towards the center of B with a speed $v_0=2 v_{\text {min }}$, where $v_m$ in is the minimum speed needed for $C$ to reach the surface of $B$. Given that $G$ is the universal gravitational constant, how does the speed $v(x)$ of C change as a function of its distance from the center of A?