A resistance $R$ and a capacitance $C$ are connected in series to a battery of negligible internal resistance through a key. The key is closed at $t = 0$. If after $t$ sec the voltage across the capacitance was seven times the voltage across $R$, the value of $t$ is\\
(1) $3RC\ln 2$\\
(2) $2RC\ln 2$\\
(3) $2RC\ln 7$\\
(4) $3RC\ln 7$