In this question you are allowed to use ONLY | (disjunction), Kleene star and concatenation and maybe parenthesis if needed. You can also use any intended characters from the question description.

a) (13) Using regular expression, specify the tokens of xyz defined as follows.

An xyz is an abc or def. An abc is a sequence of digits (from 0 to 9), and if abc has more than one digit, it never starts with 2. A def is a sequence of characters that is not started with a number digit (i.e., numbers from 0 to 9).

b) (12) Using the method discussed in the class, construct an NFA for the regular expression $a | (b^\kleene 0)$.