Between two telephone exchanges about 120 wire cables are laid underground. The telephone exchanges are 10 kms are apart.
After the wires are completely laid, someone realized that some of the wires are of the wrong type. None of the wire is labeled and cannot be distinguished visually. And hence connections at both the telephone exchanges is not possible.
You are a technician and you are asked to label the wires after identifying without ripping them all. You have a battery , bulb , pen to label, and tape with you and no transportation.
What is the shortest distance you have to travel (walk, hope you ll want it to be the shortest) to identify all the wires and label them?