Pinter Chapter 2A Question 2 is (likely) inaccurate.

[herabit]

a * ln(b) is an operation on the set of real numbers, however, the problem, at least in my copy of the book, operates on the set of all real numbers greater than zero. It is for this set, that a * ln(b) is not an operation for all possible values of a and b.

Do correct me if I am wrong here, I'm using your notes as a reference for checking my work since I can't seem to find a solution manual online for me to double-check whether I have answered correctly. Thank you for this, however, as it is helping me to verify my work.

[narodnik]

plz state the problem in full, but those html notes are copied from a site that's no longer online (but on web archive). I wrote the later .md notes.