When the source of sound moves towards a stationary observer,the wavelength of sound received by him

$A$ bat is flitting about in a cave,navigating via ultrasonic beeps. Assume that the sound emission frequency of the bat is $40\; kHz$. During one fast swoop directly toward a flat wall surface,the bat is moving at $0.03$ times the speed of sound in air. What frequency (in $kHz$) does the bat hear reflected off the wall?

$A$ car moving towards a wall at a velocity of $30 \, m/s$ sounds a horn of frequency $600 \, Hz$. What frequency $(Hz)$ will the driver hear? (Speed of sound in air = $330 \, m/s$)

$A$ person with a vibrating tuning fork of frequency $338 \,Hz$ is moving towards a vertical wall with a speed of $2 \,ms^{-1}$. The velocity of sound in air is $340 \,ms^{-1}$. The number of beats heard by that person per second is

$A$ vibrating tuning fork is moving slowly and uniformly in a horizontal circular path of radius $8 \, m$. The shortest distance of an observer in the same plane from the tuning fork is $9 \, m$. The distance between the tuning fork and the observer at the instant when the apparent frequency becomes maximum is ......... $m$.

Two vehicles,each moving with speed $u$ on the same horizontal straight road,are approaching each other. Wind blows along the road with velocity $w$. One of these vehicles blows a whistle of frequency $f_1$. An observer in the other vehicle hears the frequency of the whistle to be $f_2$. The speed of sound in still air is $V$. The correct statement$(s)$ is (are) :
$(A)$ If the wind blows from the observer to the source,$f_2 > f_1$.
$(B)$ If the wind blows from the source to the observer,$f_2 > f_1$.
$(C)$ If the wind blows from the observer to the source,$f_2 < f_1$.
$(D)$ If the wind blows from the source to the observer,$f_2 < f_1$.