A string 1.0 m long is fixed at both ends and vibrates in its second harmonic. At the same time, an open pipe 0.60 m long produces its third harmonic, and the two sounds are in unison. The string’s tension is then increased so that the wave speed on the string rises by 20 %, while the pipe length and the speed of sound in air remain unchanged. Which harmonic of the pipe will now match the frequency of the string’s fifth harmonic?
(a) 7th harmonic
(b) 9th harmonic
(c) 8th harmonic
(d) 10th harmonic