d
Switch open $C_{e}=\frac{4}{3}\, \mu F$
$\mathrm{Q}_{1}=40\, \mu \mathrm{C}$
Switch closed $C_{e}=2\, \mu F$
$\mathrm{Q}_{2}=60\, \mu \mathrm{C}$
Supply charge $=20\, \mu C$
Energy supply $=600 \times 10^{-6}=.6 \mathrm{\,ms}$
Heat loss $=.3 \mathrm{\,ms}$