My question is "Why does the book's solution state that C1 and C2 are capacitors in parallel?
I understand two things:
The capacitors in parallel mean that the capacitors are directly wired together at one plate and directly wired together at the other plate, and that the same potential difference V is applied across the two groups of wired-together plates.
The capacitors in series mean that the capacitors are wired serially, one after the other, and that a potential difference V is applied across the two ends of the series.
The heart of this problem is that I have to find the equivalent capacitor. By finding the equivalent capacitor, it's basically a single capacitor that has the same capacitance as the combination of all the capacitors in a given circuit.
Applying those two bullet point concepts above, wouldn't C3 and C2 be capacitors connected in parallel?