Answer:
Q = k M T where k is the absorption constant, Q the heat absorbed, M the mass involved and T the temperature change (for change in temperature)
Q1 = 4.18 kJ/kg * 1 kg * 273 deg K heat contained
Q2 = 4.18 kJ/kg * .5 kg * 373 deg K heat contained
Q1 = 1141 kJ deg K
Q2 = 780 kJ deg K
Q = Q1 + Q2 = 1921 kJ deg K
T = 1921 / (4.18 * 1.5) deg K = 306 deg K = (306 - 273) = 33 deg Celsius
(The total mass is now 1.5 kg)