The front compound wall of a house is decorated by wooden spheres of a 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 cm2.

r=21/2=10.5cm, SA=4πr²=4×22/7×(10.5)²=1386cm²
Cylindrical support,r1 of circular end=1.5cm,h=7cm
Curved Surface Area=2πrh=2×22/7×1.5×7=66cm²
Area of circular end=πr²=22/7×(1.5)²=7.07cm²
Area to be painted silver=8×(1386+7.07)cm²=8×1393.07cm²=11144.56cm²
Cost of silver color=Rs.0.25×11144.56=Rs.2786.14
Area to be painted black=8×66=528cm²
Cost of painting black color=528×0.05=Rs.26.40
Total cost=Rs.2786.14+26.40=Rs.2812.54