A steel wire of mass `mu` per unit length with a circular cross-section has a radius of `0.1cm`. The wire is of length `10m` when measured lying horizontal, and hangs from a hook on the wall. A mass fo `25kg` is hung from the free end of the wire. Assume the wire to be uniform and laterla strain `lt lt` logitudinal strain. If density of steel is `7860 kg m^(-3)` and Young's modulus is `2xx10^(11) N//m^(2)` then the extension in the length fo the wire is