The speed of sound in a classroom is 343 m/s. 

a) A tuning fork of frequency 512 Hz is struck. What length of open air tube is required to create a resonant sound at the 1 ^st harmonic? 

 b) For the same tube, what tuning fork frequency is needed to generate a resonant tone at the 3^rd harmonic? 

 c) In the same classroom, what is the lowest resonant frequency for a closed air tube of length 45.0 cm ?