2.9) Explain what would happen if in the capacitor given, a 3 mm thick mica sheet (of dielectric constant = 6) were inserted between the plates,(b) after the supply was disconnected.

As obtained from question number 8 charge on each plate of the capacitor is $1.771*10^{-9}C$
$V_{final}=\frac{Q}{C_{final}}=\frac{1.771\times10^{-9}}{106\times 10^{-12}}=16.7V$