A flat-plate solar collector is placed horizontally on the flat roof of a house. The collector is 5ft wide and 5ft long, and the average temperature of the exposed surface of the collector is 110 degree Fahrenheit, The emissivity of the exposed surface of the collector is 0.9. Determine the rate of heat loss fro the collector by the convection and radiation during a calm day when the ambient air temperature is 70 degree Fahrenheit and the effective sky temperature for radiation exchange is 50 degree Fahrenheit. Take the convection heat transfer coefficient on the exposed surface to be