4000ms-1
400ms-1
250ms-1
40ms-1
Correct answer is B
y = 0.005 sin[x(0.5X - 200t)]
compare to Y = A sin(kx - wt)
\(\lambda\) = \(\frac{2\pi}{k}\) and F = \(\frac{w}{2\pi}\)
V= \(\lambda\)F
= \(\frac{2\pi}{0.5}\) x \(\frac{200}{2\pi}\)
= 400ms-1