The energy stored in the capacitor is given by, Uc=21CV2. The energy stored in the inductor is given by. UL=21LI2. In LC circuit there is no loss of energy in the form of heat so, using energy conservation, Uci+ULi=Ucf+ULf
⇒21×0.2×10−6×102+0=21×0.2×10−6×52+21×0.5×10−3I2
I=3×10−1A=0.17A