Halliday, Resnick & Walker — Waves–I: Problem Problem_94

Tightening a guitar string. A guitar string with a linear density of $3.0 \text{ g/m}$ and a length of $0.80 \text{ m}$ is oscillating in the first harmonic and second harmonic as the tension is gradually increased. When the tension \(\tau\) passes through the value of \(150 \text{ N}\), what is the rate \(df/d\tau\) of the frequency change for (a) the first harmonic and (b) the second harmonic?