Water initially at 20 °C and having a mass of 100 kg is to be heated to 100°C in a boiler using charcoal as fuel. Charcoal has an energy density of 25 MJ/kg and water has a specific heat capacity of...

Extracted text: Water initially at 20 °C and having a mass of 100 kg is to be heated to 100°C in a boiler using charcoal as fuel. Charcoal has an energy density of 25 MJ/kg and water has a specific heat capacity of 4.2 kJ/kg-C. How many kilograms of charcoal is needed if the boiler efficiency is 30%? В.