From a solid sphere of mass M and radius R, a spherical portion of radius $\large\frac{R}{2}$ is removed , as shown in fig. Taking gravitational potential $V=0$ at $ r= \infty$ , the potential at the center of the cavity thus formed is:

Question

$\begin{array}{1 1} \frac{-2GM}{R} \\ \frac{-GM}{2R} \\ \frac{-GM}{R} \\ \frac{-2GM}{3R} \end{array} $