a
\(\Delta \omega=\frac{ R }{ L }\)

\(Q =\frac{\omega_0}{\Delta \omega}=\omega_0 \frac{ L }{ R }\)

\(\omega_0=\frac{1}{\sqrt{3 \times 27 \times 10^{-6}}}=\frac{1}{9 \times 10^{-3}}\)

\(\frac{ Q }{\Delta \omega}=\frac{\omega_0 \frac{ L }{ R }}{\frac{ R }{ L }}=\omega_0 \frac{ L ^2}{ R ^2}=\sqrt{\frac{1}{ LC } \frac{ L ^2}{ R ^2}}\)

\(=\frac{1}{9 \times 10^{-3}} \times \frac{9}{100}=10\,s\)