Band-Pass Gain of a filter (exercise)
Gnd symbols are too close to parts.
contrast of grids is same as pencil so hard to read.
adding brightness and contrast to photo could help us.


I only see one cap, Ca, not two Ca, Cb

The "unstated" assumption in this circuit is that the pulse width expected is much shorter than the time constant T=RaCa so for this condition, assume V(Ca) is a drifting DC voltage dependant on the duty cycle of the pulse and will always be between the pulse max~min levels, so the DC reference level Vlf will change with the signal and its gain is 1+|Av-| which for high gain 1+ can be neglected.  Taking the difference between a signal and it's LPF signal yields the HPF response when both gains are the same (assuming Av>>1 of 2nd stage.  This is an intuitive answer not mathematical such as yours which may be correct for Tpw>RaCa (low frequencies). When we want to simplify gain, we make these assumptions and state them e.g. for f>> 1/(2piRaCa) Av2= +R2/R1