Bats use echolocation to track down their prey in dark and gather information about their surroundings based on the echoes that return to them. A bat flies $7$m$/$s towards a mouse that is in ground and uses $70$ kHz of clicking sound to locate the mouse. $($Speed of sound $343$ m$/$s$)$

A$)$ what is the frequency of the echo that bat heard after reflecting it from the mouse? $($Mouse is stationary$)$

B$)$ when miuse is running away from the bat, and the bat hears back the echo frequency of $68$ kHz$,$ what will be the speed of the mouse?