A String That Is 0 $0.82 \mathrm {~m}$ Long and Open at Both Ends into Its Second Overtone

Multiple Choice

A string that is 0.15 m long and fixed at both ends is vibrating in its n = 5 harmonic. The sound from this string excites a pipe that is $0.82 \mathrm {~m}$ long and open at both ends into its second overtone resonance. What is the distance between a node and an adjacent antinode, in the string? The speed of sound in air is 345 m/s.

A) 15 mm
B) 7.5 mm
C) 23 mm
D) 30 mm
E) 150 mm