The heat loss of a glass window varies jointly as the window's area and the difference between the outside and inside temperatures. A window 5 feet by 8 feet loses 4000 Btu per
hour when the temperature outside is 20° colder than the temperature inside. Find the heat loss through a glass window that is 15 feet by 12 feet when the temperature outside is
10° colder than the temperature inside.
The heat loss is ___ Btu per hour.