you can find the derivation for the formula in the course notes. They are in the lecture “Segmentation, Targeting, Positioning”, under the quiz. Here is a link:
Hi! Thanks for your answer! But I'm sorry to say that I didn't find the explanation there. There are just formulas with no derivation. It'll be very interesting to understand more deeply where do they come from.
the formula derivations are in a separate pdf, which you can download here:
Sorry for the misunderstanding!