A musician using an open flute of length 50cm produces second...

Frequency of the observer, ${f}_{o} = 2 \times \dfrac{v}{2l} = \dfrac{330}{0.5}Hz = 660Hz$

Velocity of person$= 10km{h}^{- 1} = 10 \times \dfrac{5}{18}m{s}^{- 1} = 2.8m{s}^{- 1}$
According to Doppler effect, frequency heard by the person,

$f = {f}_{o}\dfrac{v + {v}_{0}}{v}$

$f = 660 \times \dfrac{330 + 2.8}{330}Hz = 666Hz$