Consider three options for heating a house. Electric resistance heating with electricity priced at $0.10/kWh, gas heating with gas priced at $1.10/Therm and oil (density 0.8 kg/L, heating value 46.5 MJ/kg) heating with oil priced at $1.50/gal. Energetic efficiencies are 100% for the electrical heating system, 85% for the gas heating system and 80% for the oil heating system. Determine the cost of delivering 1 GJ of energy by each system.