$A$ river $3 \,m$ deep and $40 \,m$ wide is flowing at the rate of $2 \,km$ per hour. How much water will fall into the sea in a minute (in $,m^3$)?

Find the radius of a sphere whose surface area is $154 \, cm^2$. (in $, cm$)

$A$ metal pipe is $77\, cm$ long. The inner diameter of a cross section is $4\, cm$,and the outer diameter is $4.4\, cm$. Find its inner curved surface area. (in $, cm^{2}$)

$A$ cuboidal vessel is $10 \, m$ long and $8 \, m$ wide. How high must it be made to hold $380$ cubic metres of a liquid (in $, m$)?

Find the volume of the right circular cone with radius $3.5 \, cm$,height $12 \, cm$. Assume $\pi = \frac{22}{7}$. (in $, cm^3$)

$A$ wooden bookshelf has external dimensions as follows: Height $= 110\, cm$,Depth $= 25\, cm$,Breadth $= 85\, cm$ (see Fig.). The thickness of the plank is $5\, cm$ everywhere. The external faces are to be polished and the inner faces are to be painted. If the rate of polishing is $20$ paise per $cm^2$ and the rate of painting is $10$ paise per $cm^2$,find the total expenses required for polishing and painting the surface of the bookshelf.