Mark questions with solutions in print, when not present

[rbeezer]

No description provided.

[kcrisman]

Related, maybe: "These are indicated by daggers" - but you don't indicate what that symbol looks like right there; probably it should be. I missed this on a first reading of the preface and was confused by the symbol.

Also, ideally there could be a version of the text (pdf) with solutions as well, with daggers being hyperlinks. A number of open texts (including non-MBX ones) do this.