Question 1075709
It depends on where the lights are placed.  If they are not on corners, then there would be 3 lights * 4 sides = 12 lights.  12 lights @ Rs 10 = Rs120.
However, if the lights are on the corners and in the middle, then there are 4 corners and 4 middles for a total of 8 lights.  8 lights @Rs 10 = Rs 80.