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

$\begin{array}{1 1} 8258 \\ 8516 \\ 8000 \\ 8424 \end{array}$