Hi Colleagues:
Thanks to Section 1's dedication to getting Problem 4 in good shape, I've seen I made a mistake in writing the units for kappa, the thermal conductivity. So sorry!
I will correct the Week 7 "Concepts" document ... and for now, please note that kappa has units W / (m s). (Not W / m^2 s).
This should make Problem 4 part c), work out fine in terms of units (and everything else, I hope :-).
Take care,
Amy