The amplitude of the charge oscillating in a circuit decreases exponentially as $Q = Q_0 e^{-Rt/2L}$, where $Q_0$ is the charge at $t=0s$. The time at which charge amplitude decreases to 0.50 $Q_0$ is nearly:
[Given that $R = 15 \Omega$, $L = 12 mH$, $ln(2) = 0.693$]