In a beaker with good insulation, 100g of water at 10C, 100g of copper at 100C, and 100g of ice at -10C were added. When thermal equilibrium is reached, find the amount of melted ice (for convenience of calculation, let the specific heat of water be Cw=4000J/kgC, the specific heat of ice be Ccu=400J/kgC, and the heat of melting of ice be Lf=3*10^5J/kg).

(please write the tidy solution, thank you.)