The bridge configuration shown in the figure below contains 3 known capacitors: C1 = 11.4 nF, C2 = 82.8 nF, C3 = 29.1 μF, and unknown capacitor C4. The system is charged by battery V = 18.6 V. What is charge Q4 on the unknown capacitor, when the bridge is balanced (that is, the voltmeter shown in the figure reads zero)?: Q4 = μC