2 kg of ice at −20∘C is mixed with 5 kg of water at 20∘C in an insulating vessel having a negligible heat capacity. Calculate the final mass of water remaining in the container. It is given that the specific heats of water and ice are 1 kcal/kg per ∘C and 0.5 kcal/kg/∘C while the latent heat of fusion of ice is 80 kcal/kg