Answer:
A closed organ pipe is λ/4 (node-antinode) long.
λ = speed / frequency = 331.5 / 259.6 = 1.28 m
λ/4 = .319 m length of closed pipe
An open pipe has a fundamental wavelength of A-N-A or λ/2
The second harmonic would be A-N-A-N-A or λ = 1.28 m for the second harmonic 331.5 / 259.6 = 1.28 (the fundamental would be 331.5 / .628