$\varphi =\frac{{\displaystyle 12431}}{{\displaystyle 3320}}=3.74\mathrm{eV}$

$\epsilon =\frac{\mathrm{hc}}{\lambda }=\frac{12431}{2900}=4.28\mathrm{eV}$

$(\mathrm{KE}{)}_{\max }=4.28-3.74$

$=0.54\mathrm{eV}$

Initially sphere is negatively charged so $e^{-}$ will go easily then potential becomes $O.$ After that as $e^{-}$ will leave the potential will increase till it reaches the stopping potential value, ${\mathrm{V}}_0$

$e{V}_0=0.54\mathrm{eV}$

$V_0=0.54 \mathrm{V}$