Total surface area of a closed cube with length $4 \, cm$ is $\ldots \ldots \ldots cm^{2}$.

In a right circular cone,the cross-section made by a plane parallel to the base is a

The curved surface area of a cone with radius $12 \, cm$ and slant height $20 \, cm$ is ....... $\pi \, cm^2$.

The radius of a sphere with surface area $\frac{763}{3} \, m^{2}$ is $\ldots \ldots \ldots m$. $(\pi = 3.14)$

The radii of a frustum of a cone are $10 \, cm$ and $7 \, cm$. If its height is $4 \, cm$,its curved surface area is $\dots \dots \dots \pi \, cm^2$.

$A$ container,opened from the top and made up of a metal sheet,is in the form of a frustum of a cone of height $16 \, cm$ with radii of its lower and upper ends as $8 \, cm$ and $20 \, cm$,respectively. Find the cost of the milk which can completely fill the container,at the rate of $Rs. \, 20$ per litre. Also,find the cost of the metal sheet used to make the container,if it costs $Rs. \, 8$ per $100 \, cm^2$. (Take $\pi = 3.14$)