Answer
$$
6.36 \mathrm{Hz}
$$
Work Step by Step
Using Eq. $16-26$ , we find the wave speed to be
$$
v=\sqrt{\frac{\tau}{\mu}}=\sqrt{\frac{65.2 \times 10^{6} \mathrm{N}}{3.35 \mathrm{kg} / \mathrm{m}}}=4412 \mathrm{m} / \mathrm{s}
$$
Corresponding resonant frequencies will be
$$
f_{n}=\frac{n v}{2 L}=\frac{n}{2 L} \sqrt{\frac{\tau}{\mu}}, \quad n=1,2,3, \ldots
$$
lowest (fundamental) resonant frequency $f_{1}$ is $\lambda_{1}=2 L,$ where $L=347 \mathrm{m}$ . Thus,
$$
f_{1}=\frac{v}{\lambda_{1}}=\frac{4412 \mathrm{m} / \mathrm{s}}{2(347 \mathrm{m})}=6.36 \mathrm{Hz}
$$
