2-49. Refer to Example 2-7. If the average inside temperature of this house in Virginia is increased from 65◦F to 72◦F, what is the most economical insulation amount? Assume that 100,000,000 Btu are lost with no insulation when the thermostat is set at 65◦F. The cost of electricity is now $0.086 per kWh. In addition, the cost of insulation has increased by 50%. Develop a spreadsheet to solve this problem. (2.3)