In a historical experiment to determine Planck's constant, a metal surface was irradiated with light of different wavelengths. The emitted photoelectron energies were measured by applying a stopping potential $\left(\mathrm{V}_0\right)$ are given below : Given that $\mathrm{c}=3 \times 10^8 \mathrm{~ms}^{-1}$ and $\mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$, Planck's constant (in units of J s ) found from such an experiment is