The cost of fencing a square lawn at Rs 14 per metre is Rs 28000.

Cost of fencing the lawn = Rs 28000
Let l be the length of each side of the lawn. Then, the perimeter is 4l.
We know:

Cost $=$ Rate $\times$ Perimeter

$\Rightarrow 28000=14 \times 4 \mathrm{l}$

$\Rightarrow 28000=56 l$

$O r$

$l=\frac{28000}{56}=500 \mathrm{~m}$

Area of the square lawn $=500 \times 500=250000 \mathrm{~m}^{2}$

Cost of mowing 100 m2 of the lawn = Rs 54

Cost of mowing $1 \mathrm{~m}^{2}$ of the lawn $=\mathrm{Rs} \frac{54}{100}$

$\therefore$ Cost of mowing $250000 \mathrm{~m}^{2}$ of the lawn $=\frac{250000 \times 54}{100}=$ Rs 135000