Small signal analysis of BJT dynamic microphone preamplifier
This common base operates with about 2 volts on the base. Thus Iemitter is 1.3/10K or 130 uA.
The 'reac' is 26 ohms/0.13mA == 150 ohms. Low yes, however.
The frequency response of 100uF (Cin) and 100 ohms is 0.01 second, or 16Hz.
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Regarding 'reac'
When first delighting in the use of small_signal analysis, I soon realized I could predict the gain of bipolar devices (FETs were rare, expensive, and not stable in parameters) simply by

dividing the combined Rs on the collector, in parallel

by

the series emitter resistances;

And that series emitter resistance (if no discrete external R) was just

26 ohms / Re in mA

thus a device operating at 1mA would have
'reac' of 26/1 = 26 ohms
And if that bipolar has a 260 ohm collector resistor, with only scope probe as the load, then the voltage gain was precisely

Gain = Rcollector / Remitter = Rcollector / 26 == 260/26 = 10X

And I've in the intervening decades used my personal lable 'reac' for that value, which is the slope of the emitter_base diode.
Another way to compute it is 1/tranconductance.
Again, this value is just the small_signal resistance of emitter_base diode.