A 0.35-kg coffee mug is made from a material that has a specific heat capacity of 920 J / (kg · Co) and contains 0.25 kg of water. The cup and water are at 15 oC. To make a cup of coffee, a small electric heater is immersed in the water and brings it to a boil in three minutes. Assume that the cup and water always have the same temperature and determine the minimum power rating of this heater?