To save on heating costs, the owner of a green house keeps 680 kg of water around in barrels. During a winter day, the water is heated by the sun to 11.8 °C. During the night the water freezes into ice at 0.0 °C in nine hours. What is the minimum ampere rating of an electric heating system (240 V) that would provide the same heating effect as the water does? Take the specific heat capacity of water to be 4186 J/(kg·C°), and the latent heat of fusion of water to be 3.35 x 105 J/kg.