Notes on homework 1:

For the derivation, you should follow the *pattern* of the example
on p. 91. You are using the grammar of Fig. 3.3, so you still need
to start with the start symbol of that grammar, <assignment statement>
Then each time replace exactly one nonterminal.

For the grammar (#4), the *format* of your answer should be like
Fig. 3.3. You'll have a list of productions which follow the EBNF
format. You should start with a different start symbol, however,
and the actual productions will be quite different. There is no
magic correct number of productions -- the key is to be able to
generate the desired ISBN numbers. So make sure your productions allow
you to derive:
ISBN 0-13-027678-2
ISBN 0-13-629841-9
ISBN 0-13-102857-X

(the first is the ISBN of your book, the others are for other books
from Prentice-Hall). The link on the homework should help explain
the "X" at the end of the last example.