A 4.0 Hz wave with an amplitude of 12 cm and a wavelength of 30.0 cm travels along a stretched string. (a) How far does the wave travel in a time interval of 3.0 s? m (b) How far does a knot on the string travel in the same time interval? m I got the answer to part (a) by using: x= lambda x (time/frequency) The answer I got for it was 3.6 m. I don't know what to do for part (b) Something to do with the amplitude, but I'm not sure...pls help! Thanks!