You measure the capacitance $C_{1}$ of a capacitor by doing the following: First connect capacitors $C_{1}$ and $C_{2}$ in series to a power supply that provides a voltage $V$ that can be varied. The capacitance of $C_{2}$ is known to be $3.00 \mu \mathrm{F}$. Then vary the applied voltage $V,$ and for each value of $V$ measure the voltage $V_{2}$ across $C_{2}$. After plotting your data as $V_{2}$ versus $V,$ you find that the data fall close to a straight line that has slope $0.650 .$ What is the capacitance $C_{1} ?$