An underground telephone cable consisting of a pair of identical parallel wires, has suffered a short somewhere along its length. The cable is 5 km long and in order to discover where the short is the technician first measures the resistance between the ends of two wires at one end of the cable and then at another end of the cable. (assume that nothing is connected to the cable while technician is doing that) The first measurement yields 30 Ohm, the second yields 70 Ohm. Where is the short? What is the diameter of the wire if it is made of copper?