A 2 kW, 40 litre water heater is switched on for 20 minutes. The heat capacity Cp for water is 4.2 kJ/kg K. Assuming all the electrical energy has gone into heating the water, increase of the water temperature in degree centigrade is
(a) 2.7 (b) 4.0
(c) 14.3 (d) 25.25