Bats use echolocation to hunt and navigate, emitting high frequency sounds and listening to the reflections. The range of the sounds depends on numerous factors $($including species, navigating versus hunting, and more$)$ but runs roughly from $10$ kHz to $200$ kHz$.$

The Brazilian free$-$tailed can reach speeds of almost $100$ miles per hour, so there are noticeable doppler shifts in their echolocation.$$

Suppose a bat is flying at the leisurely bat$-$speed of $17$ m$/$s$,$ and emits a$$cry at $124$kHz as it approaches a stationary object.$$

What frequency would a microphone at the stationary object detect from the bat?$$