A standing wave on a stretched string is described by $y = 4\sin\left(\dfrac{\pi x}{15}\right)\cos(96\pi t)$, where $x$ and $y$ are in centimetres and $t$ is in seconds. The amplitude of the vibration of the particle at $x = 5\ \text{cm}$, and the speed of the two travelling waves that make up this standing wave, are