The factor of an object is the ratio of its length in the direction in
which it conducts heat to the thermal conductivity of its constituent materials.

A layer of drywall has an
factor of 0.80.
An exterior wall of
a house is 4.5 m tall and
8.5 m wide. The exterior wall consists
of an exterior layer of drywall which covers a layer of fiberglass
batts that is 3.5 cm thick,
behind which is a layer of insulated
siding that has an factor of 2.1.
Determine the rate of conductive
heat loss through the wall of the house when the interior temperature
is and the exterior
temperature is .
Use a value of for
the thermal conductivity of fiberglass.