(c) Comparing with $y = a\sin{(\omega t - kx)} \Rightarrow a = \frac{10}{\pi},\omega = 2000\pi$
$\therefore v_{\max} = a\omega = \frac{10}{\pi} \times 2000\pi = 2000m/sec$
and $\omega = \frac{2\pi}{T} \Rightarrow 200\pi = \frac{2\pi}{T} \Rightarrow T = 10^{- 3}\sec$