A tent is made in the form of a frustum of a cone surmounted by another cone. The diameter of the base and the top of the frustum are $20 \mathrm{m}$ and $6 \mathrm{m}$ respectively and the height is $24 \mathrm{m}$. If the height of the tent is $28 \mathrm{m}$ and the radius of the conical part is equal to the radius of the top of the frustum, find the quantity of canvas required.