In an experiment, it is discovered that the temperature difference( in °c) between a glass of hot water and the room decreases by 4 % every minute. suppose that the original temperature of the glass of hot water is 100°c and the room temperature is 20 °c. let d °c be the temperature difference between the glass of hot water and the room after t minutes. (a) express d in terms of t. (b) find the temperature of the glass of hot water after 15 minutes, correct to the nearest °c. (c) (i) make t the subject of the equation in (a). (ii)find the time required for the temperature of the hot water to decrease to 30°c, correct to the nearest minute.