An underground telephone cable, consisting of a pair of wires, has suffered a short somewhere along its length (at point P in the Figure). The telephone cable is 4.00 km long, and in order to decide where the short is, a technician first measures the resistance among terminals AB; then he measures the resistance across the terminals CD. The first measurement yields 20.00 Ω; the second 120.00 Ω. Where is the short? Give your answer as a distance from point C. Suppose that the telephone wires are of uniform diameter.