4.The figure shows a simplified model of a house. The walls consist of layers of drywall (R-0.45).fiberglass insulation (R-11), plywood (R-0.65) and wood siding (R-0.75). The roof consists of layers of drywall(RO.45), fiberglass insulation (R-30), ply wood (R-0.65) and shingles (R-0.25). The house has 10 single-pane windows, each measuring 25 ft by 5.0 ft. Four of the windows are on the south, and each admits solar energy at the average rate of 30 Btu/(hft2). All the windows lose heat. Their R-value is 090.Assume that the house loses heat by conduction only. The average outdoor temperature in winter is 20 -F .and the house is maintained at 70 'F. The house is heated by an oil furnace that provides 100 000 Btu for every gallon of heating oil. The oil costs $2 08 per gallon. How much does it cost to heat the ho use for a month? How much is the solar gain worth?

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