A bat moving at $10 \;ms^{-1}$ towards a wall sends a sound signal of $8000\; Hz$ towards it. On reflection it hears a sound of frequency f. The value of f in Hz is close to (speed of sound = $320 \;ms^{-1}$ )$

Question

( A ) 8516
( B ) 8258
( C ) 8000
( D ) 8424