A car with a horn of frequency $620\;Hz$, travels towards a large wall with a speed $20\;m/s$. If velocity of sound is $330\;m/s$ the frequency of echo of sound of horn as heard by driver :

Question

( A ) $700 \;Hz$
( B ) $620 \;Hz$
( C ) $550 \;Hz$
( D ) $600 \;Hz$