Question 7.2: Determine the mid-band voltage gain and upper and lower cut-...

The mid-band voltage gain corresponds with the flat part of the frequency response characteristic. At that point the voltage gain reaches a maximum of 35 (see Fig. 7.12).
The voltage gain at the two cut-off frequencies can be calculated from:

A_v cut-off = 0.707 × A_v max = 0.707 × 35 = 24.7

This value of gain intercepts the frequency response graph at f_1 = 57 Hz and f_2 = 590 kHz (see Fig. 7.12).