1-12 Standing waves and resonances

A string of length 1.0 m and mass 9.0 g is fixed at one end to a vibrator and at the other end to a hanging mass through a pulley, as shown in the figure. The frequency of the vibrator is fixed at 60 Hz. Find the mass of the weight that must be hung from the string, if it is to resonate in the second harmonic.  

Example 1