Ice at 0oC is added to a copper vessel of mass 80g containing 120g of water at 30oC. If the maximum steady temperature of the mixture is 10oC, find the mass of ice melted. (Specific heat capacity of water and copper =4200 Jkg-1K-1 and 400 Jkg-1K-1,specific latent heat of ice =336000 Jkg-1)