In a Rankine cycle, regeneration results in higher efficiency because

A $$2$$ $$kW,$$ $$40$$ liter water heater is switched on for $$20$$ minutes. The heat capacity $${C_p}$$ 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