A wire of length 0.5 m and area of cross-section 4 10⁻⁶ ~m ^2 at a temperature of 100^ C is suspended vertically by fixing its upper end to the ceiling. The wire is then cooled to 0^ C , but is prevented from contracting, by attaching a mass at the lower end. If the mass of the wire is negligible, then the value of the mass attached to the wire is [Young's modulus of material of the wire =10¹¹ ~N ~m ⁻² ; coefficient