The image you provided shows a capacitor circuit with several capacitors labeled as $C_1$, $C_2$, $C_3$, and $C_4$ in a specific arrangement, with the voltage across them denoted as $V_{ab}$ and a known charge of $30.0 \, \mu C$ on $C_4$. The problem consists of three parts:

1. a) Finding the total capacitance between points $a$ and $b$.
2. b) Determining the charge on each capacitor: $C_1$, $C_2$, and $C_3$.
3. c) Finding the voltages $V_{ab}$ and $V_{ad}$.

To address these questions, I will first analyze the circuit configuration. Could you confirm if the capacitors $C_1$, $C_2$, and $C_3$ are connected in series or parallel, and how $C_4$ fits into the overall configuration? This will help determine how to proceed with solving the circuit.