Find the surface area and volume of a spherical shell, whose external and internal radii are $7 \mathrm{cm}$ and $5 \mathrm{cm}$, respectively. [Take $\mathrm{\pi }=3.14$]

The internal and external diameters of a hollow hemispherical vessel are $14 \mathrm{cm} \& 21 \mathrm{cm}$, respectively. The cost of silver plating of $1 {\mathrm{cm}}^2$ of the surface is$₹ 0.40$. Find the total cost of silver plating the vessel all over. [Take $\mathrm{\pi }=3.14$]