Explanation:

Area of hexagon = 2400√3m²
6×√3/4 a² = 2400 √3
a² = 2400 x 4 / 6
a² = 1600
a = √1600 = 40 metre
Perimeter of hexagon = 6 x 40 = 240 metre
So cost of fencing = 240 x 18.50
= Rs. 4440

Hence option 3 is the correct answer.