2 Kg of ice at -20 degree C is mixed with 5Kg of water 20 degree C in an insulating vessel having negligible heat capacity. Calculate the final mass of water remaining in the comtainer. It is given thet the specific heats of water and ice are 1Kcal/kg/degree C and 0.5Kcal/kg/degree C while latent heat of fusion of ice is 80 kcal/kg