A point source of light of power $P_0$ is placed at a distance of $4 \mathrm{m}$ from the centre of a thin hemispherical shell as shown in the figure, The shell has a radius of $3 \mathrm{m}$ and it behaves like a perfect black body. If the temperature of the hemisphere is related to the power of the source as $T^4=\frac{P_0}{n\pi \sigma }$' where $\sigma$ is the Stefan's constant, then find the value of $\frac{n}{10}$.