A steel wire of length 1 m , mass 0.1 kg and uniform cross sectional area 10−6 m2 is rigidly fixed at both ends. The temperature of the wire is lowered by 20∘ C. If the transverse waves are set up plucking the string in the middle, calculate the frequency of the fundamental mode of vibration. (Y=2×1011  n/m2,  a=1.21×10−5 / ∘ C)