The in-class exercises for Wednesday are Questions 10 and 12 in Chapter 19.

We're also offering the following extra credit in-class problem:

Estimate the monthly heating bill for a simple 20x20ft wood shack with
8ft high walls, a flat roof, and two 2x2ft windows.  The walls, door,
and ceiling are 1-inch thick white pine, and the windows are 1/4-inch
thick glass.  Assume that
  - It is 67F inside and 40F outside
  - No heat is lost through the floor
  - You have a 100% efficient electric furnace
  - You buy electricity at 10 cents per kW-hr
What fraction of the bill is from the windows?  Where would you add
insulation to get the bill down?  How much would you add?

It is worth up to 100 extra points,i.e. a complete in-class assignment.
You will have until Friday at 5pm to hand it in at the Physics office.