The amplitude and phase of a wave that is formed by the superposition of two harmonic travelling waves, \( y_1(x, t) = 4\sin(kx - \omega t) \) and \( y_2(x, t) = 2\sin(kx - \omega t + \frac{2\pi}{3}) \), are:
$[\sqrt{3}, \frac{\pi}{6}]$
$[2\sqrt{3}, \frac{\pi}{6}]$
$[6, \frac{\pi}{3}]$
$[6, \frac{2\pi}{3}]$