\(I_0 = q_0.\omega = 10^{-9}.10^4= 10^{-5}A.\)
\(\left(\frac{q}{q_0}\right)^2+\left(\frac{i}{I_0}\right)^2=1\)
=> \(\left(\frac{q}{q_0}\right)^2 = 1-\left(\frac{i}{I_0}\right)^2 = 1-\left(\frac{6.10^{-6}}{10^{-5}}\right)^2= \frac{16}{25} \)
=> \(q = q_0.\frac{4}{5} = 8.10^{-10}C.\)