Two waves are generated on a string of length $9m$ to produce a standing wave with $4$ nodes $($not including the ends$)$ with an amplitude of $6cm.$ The wave speed is $125\frac{m}{s}.$

Let the equation for one of the wave be of the form: $y(x,t)=$Asin$(kx-t).$ In the equation for the other wave, what are:

a$.$ The amplitude $($in $cm)$

b$.$ The wavenumber $($in $\frac{1}{m})$

c$.$ The angular frequency $($in $1/$s$,$ including sign$)$