 OK, in this problem, 311, we're trying to calculate the heat loss through a 150-day heating season in Roanoke, Virginia. It is a 150-day heating season. The outside temperature is given as 47 degrees Fahrenheit. Inside is, obviously, 65 degrees Fahrenheit, OK? Degree days can be calculated like this. Heating degree days are equal to number of days, which is 150 in a season here, times the temperature difference, 65 minus 47 degrees Fahrenheit. Now we can calculate that. That is equal to 150 times 18. So that turns out to be 2,700 degrees Fahrenheit days. Now what else do we need? We need the area. Area is given, area is equal to 176 foot square, and we are also given the r value. r value is 16. Therefore we can calculate the heat loss. Heat loss through a season, heat loss through the season is equal to area times HDD times 24 over r, 176 foot square. Here it is 2,700 degrees Fahrenheit days times 24 hours in a day divided by r value of 16 foot square, degrees Fahrenheit, hour over days. What can we cancel? Foot square, foot square, degrees Fahrenheit, hour and hour, days in days are canceled. So when we do this calculation here, we get the answer of 712,800 or 712,800 BTUs in this 150 day heating season.