$A$ cuboidal closed tank of iron sheet is made having $10 \, m$ length,$8 \, m$ breadth,and $3 \, m$ height. Determine the cost of iron sheet used at the rate of $₹ 50$ per $m^2$. (in $₹$)

$A$ cuboidal box measures $25 \, cm \times 15 \, cm \times 8 \, cm$. Find its total surface area (in $cm^2$).

The radius and slant height of a cone are $10 \, cm$ and $25 \, cm$ respectively. Find the total surface area of a cone. (in $cm^2$)

The curved surface area of a hemisphere is $306 \, cm^{2}$. Then its total surface area is $\dots \dots \dots cm^{2}$.

The front compound wall of a house is decorated by wooden spheres of diameter $21\, cm,$ placed on small supports as shown in the figure. Eight such spheres are used for this purpose,and are to be painted silver. Each support is a cylinder of radius $1.5\, cm$ and height $7\, cm$ and is to be painted black. Find the cost of paint required if silver paint costs $25$ paise per $cm^{2}$ and black paint costs $5$ paise per $cm^{2}.$

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