$(F = 96500 \,C\, mol^{-1})$
For the cell reaction,
$2 \mathrm{Ag}^{+}+\mathrm{Cu} \rightarrow \mathrm{Cu}^{2+}+2 \mathrm{Ag}$
$\Delta E^{\circ}$ cell $=+0.46 \mathrm{V}$
$\Delta \mathrm{G}^{\circ}=-2 \times 96500 \times 0.46$
$=-88780 \mathrm{J}$
$=-88.7 \mathrm{kJ}$
$=-89.0 \mathrm{kJ}$