Correct Answer - ₹ 16800
Length of a room `=20ft`
Breadth of a room `=15ft`
Height of a room `=12ft`
Area of the 4 walls of the room =Lateral surface area of the room `=2(l+b)h`
`=2(20+15)12`
`=24(35)=840sq.ft`
The cost of painting the walls of the room at` ₹20` per sq.ft
`=840xx₹ 20 = ₹ 16800`