b
(b) From the given equation amplitude \(a = 0.04m\)

Frequency \( = \frac{{{\rm{Co}} - {\rm{efficient of t}}}}{{2\pi }}\)

 \( = \frac{{\pi /5}}{{2\pi }} = \frac{1}{{10}}Hz\)

Wave length \(\lambda = \frac{{2\pi }}{{{\rm{Co}} - {\rm{efficient}}\;of\;x}}\)

\( = \frac{{2\pi }}{{\pi /9}}=18m.\)

Wave speed \(v = \frac{{{\rm{Co - efficient of }}t}}{{{\rm{Co - efficient of }}x}}\)

\( = \frac{{\pi /5}}{{\pi /9}} = 1.8m/s.\)