A motor generates transverse waves in a mechanical wave machine. During 6.0 s, the motor makes 42 complete oscillations. A video frame shows one crest at the 0.40 m position and the fifth crest after it at the 3.90 m position. What is the wave speed?
4.1 m/s4.1\ \mathrm{m/s}4.1 m/s
0.10 m/s0.10\ \mathrm{m/s}0.10 m/s
25 m/s25\ \mathrm{m/s}25 m/s
4.9 m/s4.9\ \mathrm{m/s}4.9 m/s