A 100- \(\mu \mathrm{F}\) capacitor has no voltage across it at \(t=0\). A current flowing through the capacitor is given as \(i_{\mathrm{C}}(t)=2 u(t\) )\(-3 u(t-3)+u(t-6) \mathrm{mA}\). Find the voltage across the capacitor at \(t=4 \mathrm{~s}\). Repeat for \(t=6 \mathrm{~s}\).