How did you experimentally find the mass of the string? options: It was the slope of the . v s . ( f n

How did you experimentally find the mass of the string?  options:

1. It was the slope of the τ . v s . ( f n ) 2 plot (where T is the tension and f is the frequency of vibration)
2. 
   
3. It was the slope of the plot divided by L, the length of the string
4. 
   
5. It was the slope divided by 2L
6. 
   
7. It was the slope divided by 4L