A calorimeter has 9g of water at 30°C initially. Some amount of ice at -20° C is mixed with water in the calorimeter and the final temperature of the mixture is found to be 5°C. If the water equivalent of the calorimeter is 10 g then the amount of the ice mixed was? (Take, sw = 1 cal/g°C, sice = 0.5 cal/g°C and Lf of ice = 80 cal/g)