 This problem is very similar to the last one 311. Now this 312 involves again heat loss through a season. We need to calculate the HDDs and the heat the days heating degrees or 220 days. Now the temperature difference is inside 265 degrees Fahrenheit as usual and outside the temperature average temperature happens to be 27 for all 220 days Therefore heating degree days can be calculated like this 220 days times 65 minus 27 degrees Fahrenheit and This is equal to 220 days times 38 degrees Fahrenheit, which is equal to 8,360 Do we know the area? Area is given actually The dimensions of the window are 8 feet by 6 feet Therefore the area is 8 feet times 6 feet, which is 48 Square feet We know the temperature difference. We know the heating degree days We need we can calculate the heat loss provided we have the R value. R value is also given 1 foot squared degree Fahrenheit hour over BTU Now it's easy to calculate heat loss heat loss Through a season is equal to area And I'm trying to repeat this area times HDD times 24 over R So in this case it is area is 48 square feet and we have 8,360 degrees days times 24 hours over a day divided by R value of 1 foot squared degrees Fahrenheit hour over BTU So foot squared foot squared degrees Fahrenheit degrees Fahrenheit can be cancelled hours and hours are cancelled Days and days are cancelled here So when you do this math, it comes out to be 9,630,720 BTUs This is in one full season