The answers

Warning: The answers must be entered in exactly the way spelled out here. This aspect of ans.sty is very user-unfriendly. Deviation will result in answers appearing in the text or part of the next problem appearing in the answer.

The answer should start immediately after the exercise without a blank line intervening, preceded by the word answer. You can type anything you want in the answer, subject to the following three requirements:

If you want more than one paragraph in an answer, insert the command par at the end of each paragraph except the last.

The reason for these requirements is that the program uses the blank line to delimit the answers (using an idea of Donald Knuth's).