${z_1} = a\cos (kx - \omega \,t)$.....$(A)$
${z_2} = a\cos (kx + \omega \,t)$.....$(B)$
${z_3} = a\cos (ky - \omega \,t)$..... $(C)$
$(A)$ The speed of sound determined from this experiment is $332 m s ^{-1}$
$(B)$ The end correction in this experiment is $0.9 cm$
$(C)$ The wavelength of the sound wave is $66.4 cm$
$(D)$ The resonance at $50.7 cm$ corresponds to the fundamental harmonic