The dimensions of a room are $14m\times 10m\times 6.5m$. There are two doors and 4 windows in the room. Each door measures $2.5m\times 1.2m$ and each window measures $1.5\times 1m$. Find the cost of painting the four walls of the room at RS 35 per $m^2$.

Cost = RS 35 per $m^2$
Now,
Area of four walls $=$ 2(Length of walls $\times$  Height of walls) $+2$(Breadth of walls $\times$ Height of walls)
$=2(14\times 6.5)+2(10\times 6.5)$
$=182+130$
$=312$
$\Rightarrow$ Area of four walls is $312m^2$

Area of two doors $=$ 2(Length of doors $\times$ Breadth of doors)
$=2(2.5\times 1.2)$
$=6$
$\Rightarrow$ Area of two doors is $6m^2$

Area of four windows $=$ 4(Length of windows $\times$ Breadth of windows)
$=4(1.5\times 1)$
$=6$
$\Rightarrow$ Area of four windows is $6m^2$

Therefore,
Area to be painted $=$ Area of 4 walls $-$ (Area of 2 doors $+$ Area of 4 windows)
$=312(6+6)$
$=300$
$\Rightarrow$ Area to be painted is $300m^2$

Cost of painting $=300m^2\times$ Rs 35 per $m^2$
$=Rs10500$