\(C_{\text {eff }} \frac{2 c}{3} q\)

\(=\frac{2 c }{3} \times 50\)

\(=\frac{5}{2} \times 10^{-4}\)

\(=1.66 \times 10^{-4}\,C\)

After the switch is made on

Then,

\(c_{\text {eff }}=2 c =10^{-6}\)

\(Q=10^{-6} \times 50\)

\(=5 \times 10^{-4}\,C\)

Now the initial charge will remain stored and in the stored in the short capacitor

Therefore,

Net charge flowing is

\(5 \times 10^{-4}-1.66 \times 10^{-4}\)

\(=3.3 \times 10^{-4}\,C\)

Hence, the net charge flows is \(3.3 \times 10^{-4}\,C\)