Answer:
You are the one who will answer that because you will experiment
Density =mass/volume 120/200 =0.6 g/cm
The velocity of the wave on the string is given by

Solving the above equation,

The frequency of the wave
and wave length is 
The velocity is 
Substituting numerical values,

The length of the string is 
By someone wearing them doing some exhilarating thing