Inside a parallel-plate capacitor there is a plate parallel to the outer plates, whose thickness is equal to `eta = 0.60` of the gap width. When the plates is absent the capacitor cpaacitance equals `c = 20 muF` . First, the capacitor was connected in parallel to a constant voltage source producting `V = 200 V`, then it was disconnected for it, after which the plates was slowly removed from teh gap. FInd the work perfomed during the removel, if the plate is
(a) made of metal, (b) made of glass.