A uniformly charged solid sphere of radius R has potential V0 (measured with respect to ∞) on its surface. For this sphere, the equipotential sufaces, with potentials $\frac{3V_{0}}{2},\frac{5V_{0}}{4},\frac{3V_{0}}{4} and \frac{V_{0}}{4}$ have radius R1, R2 ,R3 and R4 respectively. Then R4