The inner diameter of a circular well is $3.5\, m$. It is $10\, m$ deep. Find the cost of plastering this curved surface at the rate of $Rs. 40$ per $m^2$.

The capacity of a cuboidal tank is $50000$ litres of water. Find the breadth of the tank,if its length and depth are respectively $2.5\, m$ and $10\, m$. (in $, m$)

$A$ conical pit of top diameter $3.5 \, m$ is $12 \, m$ deep. What is its capacity in kilolitres (in $kl$)?

Find $(i)$ the curved surface area and $(ii)$ the total surface area of a hemisphere of radius $21\, cm$.

$A$ capsule of medicine is in the shape of a sphere of diameter $3.5 \, mm$. How much medicine (in $mm^3$) is needed to fill this capsule (in $, mm^3$)?

$A$ small indoor greenhouse (herbarium) is made entirely of glass panes (including base) held together with tape. It is $30 \, cm$ long,$25 \, cm$ wide and $25 \, cm$ high. What is the area of the glass (in $, cm^2$)?