A telephone switchboard 100 pair cable can be made up with either enameled wire or tinned wire. There will be 400 soldered connections. The cost of soldering a connection on the enameled wire will be P 1.65 on the tinned wire, it will be P 1.15. A 100- pair cable made up with enameled wire cost P 0.55 per linear foot and those made up of tinned wire cost P 0.75 per linear foot. Determine the length of cable run in feet so that the cost of each installation would be the same ?