The capacity of a closed cylindrical vessel of height $1 \, m$ is $15.4$ litres. How many square metres of metal sheet would be needed to make it (in $, m^{2}$)?

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 $m^2$.

Find the surface area of a sphere with a diameter of $3.5 \, cm$. Assume $\pi = \frac{22}{7}$. (in $, cm^2$)

The height and the slant height of a cone are $21 \, cm$ and $28 \, cm$ respectively. Find the volume of the cone. (in $, cm^3$)

$A$ bus stop is barricaded from the remaining part of the road by using $50$ hollow cones made of recycled cardboard. Each cone has a base diameter of $40 \, cm$ and height $1 \, m$. If the outer side of each of the cones is to be painted and the cost of painting is $Rs. 12$ per $m^2$,what will be the cost of painting all these cones? (Use $\pi = 3.14$ and take $\sqrt{1.04} = 1.02$)

The height of a cone is $16 \, cm$ and its base radius is $12 \, cm$. Find the curved surface area and the total surface area of the cone (Use $\pi = 3.14$). (in $, cm^2$)