The surface area of a cube whose edge is $a$ is: (in $a^{2}$)

Find the surface area of a sphere of diameter $3.5\,m$ (in $m^2$).

Curved surface area of a hemisphere $= \ldots \ldots \ldots$

The total surface area of a closed cylinder is $748\, cm^2$. If its radius is $7\, cm$,find its height (in $cm$).

$A$ heap of wheat is in the form of a cone whose diameter is $42 \, m$ and height is $20 \, m$. The heap is to be covered by canvas to protect it from rain. If the price of canvas is $₹ 75$ per $m^2$,find the cost of the canvas required.

Two cubes each of $8 \, cm$ edge are joined end to end. Find the total surface area of the cuboid so formed (in $cm^{2}$).