A person makes a quantity of iced tea by mixing 500g of hot tea (basically water) with an equal mass of ice at its melting point. Suppose the mixture has negligible energy exchanges with its environment. If the tea's initial temperature is Ti = 90 degrees Celsius, when thermal equilibrium is reached what are (a) the mixture's temperature Tf and (b) the remaining mass mf of ice? If Ti = 70 degrees Celsius, when thermal equilibrium is reached what are (c) Tf and (d) mf?