Wave equation: \( y = 8 \sin (0.02 x - 4 t) \).
Standard form: \( y = A \sin (kx - \omega t) \).
\[
k = 0.02 \, \text{cm}^{-1}, \quad \omega = 4 \, \text{s}^{-1}.
\]
Wave speed: \( v = \frac{\omega}{k} = \frac{4}{0.02} = \frac{4 \cdot 100}{2} = 200 \, \text{cm/s}.
Answer: 200 cm/s.