A travelling wave is described by the equation \( y(x,t) = [0.05 \sin(8x - 4t)] \, \text{m} \). The velocity of the wave is : [all the quantities are in SI unit]
\( 2 \, \text{m} \, \text{s}^{-1} \)
\( 4 \, \text{m} \, \text{s}^{-1} \)
\( 0.5 \, \text{m} \, \text{s}^{-1} \)
\( 8 \, \text{m} \, \text{s}^{-1} \)