10. (20 points) A solar collector provides the hot water needs of a family for a period of 7 months except for 5 months of winter season. The collector supplies hot water at an average temperature of 55C and the average temperature of cold water is 18C. An examination of water bills indicates that the family uses an average of 15 tons of hot water from the solar collector per month. An electrical resistance heater supplies hot water in winter months. The cost of electricity is $0.13/kWh and the efficiency of the electric heater can be taken to be 93% considering heat losses from the system. Determine the annual electricity and cost savings to this family due to solar collector. (specific heat of water at room temperature: 4.18kJ/kgC )