A waste heat source is available at 400°C. A heat engine operates using heat from this source. It rejects heat to the surroundings at 38°C. The power from the engine runs an air conditioner to keep the air inside a building at 25°C, rejecting heat to the surroundings at 38°C. Heat leaks into the building at the rate of 1 kW per degree temperature difference between the surroundings and the temperature inside the building. What is the minimum required heat transfer rate from the waste heat source? Five stars to explain relationships of the formulas as you go.