Q6.  While the length is kept constant, the fundamental frequency of a sonometer wire increases by 6Hz on increasing the tension by 44% . Now if original tension in wire is kept constant, find the decrease in fundamental frequency of wire, when length of wire is increased by 20%
        (A) 15Hz               ​(B) 6Hz    ​            ​(C) 11Hz                ​(D) 5Hz