One String on a Guitar Is Exactly in Tune

Multiple Choice

One string on a guitar is exactly in tune.The guitarist uses this string to produce a tone with a frequency of 196 Hz by pressing down at the proper fret.An adjacent string can also be used to produce this tone without being pressed against a fret.However,this adjacent string is out of tune and produces a tone that sounds lower in frequency than the other tone.When the tones are produced simultaneously,the beat frequency is 5.0 Hz.What frequency does the adjacent string produce?

A) 196 Hz
B) 191 Hz
C) 171 Hz
D) 201 Hz
E) 186 Hz