Hello,
Just a note that in the problem set of ex 6 in hw 1, one missing "axiom" is that P goes from F to [0,1] (this axiom is present in the lecture notes). It is needed to prove the listed properties. To be more precise, what is need is that P is non-negative.
All the best,
Olivier
PS: Hw 2 is already online, in case some of you would like to work in advance...