When human vocal cords are used to sing falsetto, the result is a very pure sound, relatively free of overtones. Assume two singers are singing falsetto, attempting to produce a note with frequency 4080 hertz, but a beat frequency of 8 Hz is heard
a.) By how many hertz is the frequency of the sound produced by the lower note lower than the frequency of the combined sound?
b.) By how many hertz is the frequency of the sound produced by the higher note higher than the frequency of the combined sound?