A capacitor for high voltage consists of 180 sheets of glass, square, 1.2 m side, of relative dielectric constant K=2 and thickness e=6mm, which separate 181 metal sheets alternately joined together. This capacitor is discharged by melting 0.25gr of lead from a fuse initially at 20∘C. The melting temperature of lead is 327∘C, its heat of fusion is 5.92 cal/gr and the specific heat 0.031cal/gr.∘C. Calculate the initial potential difference between the armatures of that capacitor.