$${Q_\text{soojendamine} = cm\Delta t = 4200 \, \frac{\text{J}}{\text{kg}^\circ \text{C}} \cdot 0,2 \, \text{kg} \cdot 80\, ^\circ \text{C} = 67200\, \text{J} = 67,2\, \text{kJ}}$$