Specific heat of ice is 2.1\\ J/g{}^oC Total heat released by water is 10\ imes 4.2\ imes50=2100\\ J Total heat absorbed by ice from -20^oC\\ to\\ 0^oC=10\ imes2.1\ imes20=420\\ J \\Delta Q=2100-420=mL Melted ice, m=(2100-420)/336\\approx5gm Hence, at equilibrium, total water is 15g , total ice is 5g .