Solution:
Given that, the rectangular lawn 115m by 64 m has two roads one 2 m wide running through parallel to its length and the other 2.5m wide parallel to its breadth.The area of the roads = Area of road parallel to length + area of road parallel to breadth – area of common road.
Calculating the cost of gravelling the road = Area of the roads ₹60 per .
The construction cost in total is ₹23100.
Therefore, option 2 is correct.