(a) The maximum particle velocity are twice the wave velocity
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ a\omega = 2\left( \frac{\omega}{k} \right)$
Or ak=2
Given y=a sin 2π(b+-cx)
Or y=a sin (2πbt-2πcx)
The general wave can
Y=a sin (ωt-x)
Then k=2πc
So, $a_{2}\pi c = 2$
$c = 1/\pi a$