Someone had asked last class if there was a way to get the step-by-step instructions that we went over in class today.
(the only slight point I'd pick on is that the author doesn't appreciate that the sling of an endogenous variable is already the conditional (i.e. error) variance.
(I've not gone over all of them, obviously, so I can't vouch for them but they look reasonable).
FWIW. Phil