Resonant modes on a String

A string with mass per unit length $\mu = 2$ g/m is stretched between a 60 Hz oscillator and a clamp 1.5 meters away. The string is under a tension $T = Mg$ produced by a weight suspended from the string as shown (you may use $g = 10$ m/sec$^2$ if you wish).

a) What must mass $M$ be to drive a resonance with the standing wave pattern shown above?

b) What is the velocity of waves in the string at that time?

c) If the mass $M$ from part a) is left unchanged on the string, what frequency $f$ must the oscillator be changed to to excite the fundamental harmonic?