Physics Question from JEE Main 2023 · 10 April, Shift 1

Three concentric spherical metallic shells X, Y, and Z of radii $a$, $b$, and $c$ respectively ($a < b < c$) have surface charge densities $\sigma$, $-\sigma$, and $\sigma$ respectively. The shells X and Z are at the same potential. If the radii of X and Y are $2 \, \text{cm}$ and $3 \, \text{cm}$ respectively, the radius of shell Z is: