A $60\mathrm{}\mathrm{p}\mathrm{F}$ capacitor is fully charged by a $20\mathrm{}\mathrm{V}$ supply. It is then disconnected from the supply and is connected to another uncharged $60\mathrm{}\mathrm{p}\mathrm{F}$ capacitor in parallel. The electrostatic energy that is lost in this process by the time the charge is redistributed between them is (in $\mathrm{n}\mathrm{J}$ ) ________