Question: How much should I charge for my ebook?

Definitely less than the printed version (if there is one). Besides that, there is no definite answer to this. I suggest searching for ebooks that you would consider "competitors" to yours. Identify those of similar size (number of pages), and price your ebook competitively with theirs.

As a rule of thumb, $2.99 - 9.99 is an ideal price for most ebooks.