Help with Compile and File Size

Hi All,

I had a book that included about 80 scanned documents. My file size was near 400mb - bad for ebook. So I deleted all scanned files and retyped (manually). Not sure I like that idea, but my file is now near 28mb. When I convert to .mobi - the file goes up to nearly 36mb - which for an amazon book is about $5.40 in costs just for file size - that is not acceptable. What do I do to shrink the file size?
Someone suggested using calibre. What is best way to get my scrivener file (now with 5 images that are each 200-400kb) down to under 10mb. The book is only 190 pages.

Thanks
Denise