c
$y=0.03 \sin \left[450\left(t-\frac{9 x}{450}\right)\right]$
So, $\mathrm{v}=\frac{450}{9}=50 \mathrm{m} / \mathrm{s}$
Also, $v=\sqrt{\frac{T}{\lambda}}$
$\Rightarrow 50=\sqrt{\frac{T}{5 \times 10^{-3}}}$
$\Rightarrow T=2500 \times 5 \times 10^{-3}=12.5 \mathrm{N}$