Merge pull request #59 from Dick-Lane/master

1 new fix; I'm confused
The problem now accepts any capitalization.
Warning about the hint mentioning a section in the book is added.
Change domain of function evaluation

Context()->variables->set(t => {limits => [900, 1100]});
This will make the answer checker more robust.
Change domain of function evaluation

See Lebl-1-4-09b.pg
This is a suggestion for improving readability of this problem.
(It is NOT a fix of any bug.)

Enlarge figures
 a) large view of candidate graphs
 b) thumbnails of candidate graphs
 c) graph of correct answer in solution
 d) graph of original function