At t = 0, three successive crests on a stretched string are located at x = 1.1 m, 3.5 m and 5.9 m. At the point x = 0.5 m, successive troughs are observed at t = 0.12 s, 0.32 s and 0.52 s. Assuming a progressive sinusoidal wave, determine its speed.
(a) 6m s−1
(b) 12m s−1
(c) 8m s−1
(d) 10m s−1